diff --git a/pkg/apis/config/defaults.go b/pkg/apis/config/defaults.go
index d3a724d7333..c3b06be5344 100644
--- a/pkg/apis/config/defaults.go
+++ b/pkg/apis/config/defaults.go
@@ -181,13 +181,11 @@ func getBrokerClasses(d *Defaults) map[string]*BrokerConfigSpec {
 
 // matchBrokerClass find the corresponding brokerConfig for a given brokerClass
 func matchBrokerClass(brokerClass string, brokerClasses map[string]*BrokerConfigSpec) *BrokerConfig {
-	for bClass, bCSpec := range brokerClasses {
-		if bClass == brokerClass {
-			var bConfig BrokerConfig
-			bConfig.KReference = bCSpec.Spec.Config
-			bConfig.Delivery = bCSpec.Spec.Delivery
-			return &bConfig
-		}
+	var bConfig BrokerConfig
+	if bCSpec, ok := brokerClasses[brokerClass]; ok {
+		bConfig.KReference = bCSpec.Spec.Config
+		bConfig.Delivery = bCSpec.Spec.Delivery
+		return &bConfig
 	}
 	return nil
 }
diff --git a/pkg/apis/eventing/v1/broker_defaults_test.go b/pkg/apis/eventing/v1/broker_defaults_test.go
index 4f341a68a44..630b608348f 100644
--- a/pkg/apis/eventing/v1/broker_defaults_test.go
+++ b/pkg/apis/eventing/v1/broker_defaults_test.go
@@ -34,7 +34,7 @@ import (
 )
 
 var (
-	defaultConfig = &config.Config{
+	defaultConfig1 = &config.Config{
 		Defaults: &config.Defaults{
 			// NamespaceDefaultsConfig are the default Broker Configs for each namespace.
 			// Namespace is the key, the value is the KReference to the config.
@@ -56,9 +56,9 @@ var (
 									APIVersion: "serving.knative.dev/v1",
 								},
 							},
-							Retry:         pointer.Int32Ptr(5),
-							BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.StringPtr("exponential")),
-							BackoffDelay:  pointer.StringPtr("5s"),
+							Retry:         pointer.Int32(5),
+							BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("exponential")),
+							BackoffDelay:  pointer.String("5s"),
 						},
 					},
 				},
@@ -80,9 +80,9 @@ var (
 									APIVersion: "serving.knative.dev/v1",
 								},
 							},
-							Retry:         pointer.Int32Ptr(3),
-							BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.StringPtr("exponential")),
-							BackoffDelay:  pointer.StringPtr("3s"),
+							Retry:         pointer.Int32(3),
+							BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("exponential")),
+							BackoffDelay:  pointer.String("3s"),
 						},
 					},
 				},
@@ -103,9 +103,9 @@ var (
 									APIVersion: "serving.knative.dev/v1",
 								},
 							},
-							Retry:         pointer.Int32Ptr(5),
-							BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.StringPtr("linear")),
-							BackoffDelay:  pointer.StringPtr("5s"),
+							Retry:         pointer.Int32(5),
+							BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("linear")),
+							BackoffDelay:  pointer.String("5s"),
 						},
 					},
 				},
@@ -128,14 +128,56 @@ var (
 								APIVersion: "serving.knative.dev/v1",
 							},
 						},
-						Retry:         pointer.Int32Ptr(3),
-						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.StringPtr("exponential")),
-						BackoffDelay:  pointer.StringPtr("5s"),
+						Retry:         pointer.Int32(3),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("exponential")),
+						BackoffDelay:  pointer.String("5s"),
 					},
 				},
 			},
 		},
 	}
+
+	defaultConfig2 = &config.Config{
+		Defaults: &config.Defaults{
+			// NamespaceDefaultsConfig are the default Broker Configs for each namespace.
+			// Namespace is the key, the value is the KReference to the config.
+			NamespaceDefaultsConfig: map[string]*config.ClassAndBrokerConfig{
+				"mynamespace1": {
+					BrokerClass: "KafkaBroker",
+					BrokerConfig: &config.BrokerConfig{
+						KReference: &duckv1.KReference{
+							APIVersion: "v1",
+							Kind:       "ConfigMap",
+							Namespace:  "knative-eventing",
+							Name:       "kafka-channel",
+						},
+						Delivery: &eventingduckv1.DeliverySpec{
+							DeadLetterSink: &duckv1.Destination{
+								Ref: &duckv1.KReference{
+									Kind:       "Service",
+									Namespace:  "default",
+									Name:       "handle-error",
+									APIVersion: "serving.knative.dev/v1",
+								},
+							},
+							Retry:         pointer.Int32(5),
+							BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("exponential")),
+							BackoffDelay:  pointer.String("5s"),
+						},
+					},
+				},
+				"mynamespace2": {
+					BrokerClass: "RabbitmqBroker",
+				},
+				"mynamespace3": {
+					BrokerClass: "KafkaBroker",
+				},
+			},
+			ClusterDefault: &config.ClassAndBrokerConfig{
+				BrokerClass: eventing.MTChannelBrokerClassValue,
+			},
+		},
+	}
 )
 
 func TestBrokerSetDefaults(t *testing.T) {
@@ -166,9 +208,9 @@ func TestBrokerSetDefaults(t *testing.T) {
 								APIVersion: "serving.knative.dev/v1",
 							},
 						},
-						Retry:         pointer.Int32Ptr(3),
-						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.StringPtr("exponential")),
-						BackoffDelay:  pointer.StringPtr("5s"),
+						Retry:         pointer.Int32(3),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("exponential")),
+						BackoffDelay:  pointer.String("5s"),
 					},
 				},
 			},
@@ -196,9 +238,9 @@ func TestBrokerSetDefaults(t *testing.T) {
 								APIVersion: "serving.knative.dev/v1",
 							},
 						},
-						Retry:         pointer.Int32Ptr(3),
-						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.StringPtr("exponential")),
-						BackoffDelay:  pointer.StringPtr("5s"),
+						Retry:         pointer.Int32(3),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("exponential")),
+						BackoffDelay:  pointer.String("5s"),
 					},
 				},
 			},
@@ -242,9 +284,9 @@ func TestBrokerSetDefaults(t *testing.T) {
 								APIVersion: "serving.knative.dev/v1",
 							},
 						},
-						Retry:         pointer.Int32Ptr(3),
-						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.StringPtr("exponential")),
-						BackoffDelay:  pointer.StringPtr("5s"),
+						Retry:         pointer.Int32(3),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("exponential")),
+						BackoffDelay:  pointer.String("5s"),
 					},
 				},
 			},
@@ -276,9 +318,9 @@ func TestBrokerSetDefaults(t *testing.T) {
 								APIVersion: "serving.knative.dev/v1",
 							},
 						},
-						Retry:         pointer.Int32Ptr(5),
-						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.StringPtr("exponential")),
-						BackoffDelay:  pointer.StringPtr("5s"),
+						Retry:         pointer.Int32(5),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("exponential")),
+						BackoffDelay:  pointer.String("5s"),
 					},
 				},
 			},
@@ -310,9 +352,9 @@ func TestBrokerSetDefaults(t *testing.T) {
 								APIVersion: "serving.knative.dev/v1",
 							},
 						},
-						Retry:         pointer.Int32Ptr(5),
-						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.StringPtr("linear")),
-						BackoffDelay:  pointer.StringPtr("5s"),
+						Retry:         pointer.Int32(5),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("linear")),
+						BackoffDelay:  pointer.String("5s"),
 					},
 				},
 			},
@@ -344,9 +386,9 @@ func TestBrokerSetDefaults(t *testing.T) {
 								APIVersion: "serving.knative.dev/v1",
 							},
 						},
-						Retry:         pointer.Int32Ptr(3),
-						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.StringPtr("exponential")),
-						BackoffDelay:  pointer.StringPtr("3s"),
+						Retry:         pointer.Int32(3),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("exponential")),
+						BackoffDelay:  pointer.String("3s"),
 					},
 				},
 			},
@@ -369,9 +411,9 @@ func TestBrokerSetDefaults(t *testing.T) {
 								APIVersion: "serving.knative.dev/v1",
 							},
 						},
-						Retry:         pointer.Int32Ptr(5),
-						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.StringPtr("linear")),
-						BackoffDelay:  pointer.StringPtr("5s"),
+						Retry:         pointer.Int32(5),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("linear")),
+						BackoffDelay:  pointer.String("5s"),
 					},
 				},
 			},
@@ -399,9 +441,9 @@ func TestBrokerSetDefaults(t *testing.T) {
 								APIVersion: "serving.knative.dev/v1",
 							},
 						},
-						Retry:         pointer.Int32Ptr(5),
-						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.StringPtr("linear")),
-						BackoffDelay:  pointer.StringPtr("5s"),
+						Retry:         pointer.Int32(5),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("linear")),
+						BackoffDelay:  pointer.String("5s"),
 					},
 				},
 			},
@@ -424,9 +466,9 @@ func TestBrokerSetDefaults(t *testing.T) {
 								APIVersion: "serving.knative.dev/v1",
 							},
 						},
-						Retry:         pointer.Int32Ptr(5),
-						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.StringPtr("linear")),
-						BackoffDelay:  pointer.StringPtr("5s"),
+						Retry:         pointer.Int32(5),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("linear")),
+						BackoffDelay:  pointer.String("5s"),
 					},
 				},
 			},
@@ -454,9 +496,271 @@ func TestBrokerSetDefaults(t *testing.T) {
 								APIVersion: "serving.knative.dev/v1",
 							},
 						},
-						Retry:         pointer.Int32Ptr(5),
-						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.StringPtr("linear")),
-						BackoffDelay:  pointer.StringPtr("5s"),
+						Retry:         pointer.Int32(5),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("linear")),
+						BackoffDelay:  pointer.String("5s"),
+					},
+				},
+			},
+		},
+	}
+	for n, tc := range testCases {
+		t.Run(n, func(t *testing.T) {
+			tc.initial.SetDefaults(config.ToContext(context.Background(), defaultConfig1))
+			if diff := cmp.Diff(tc.expected, tc.initial); diff != "" {
+				t.Fatal("Unexpected defaults (-want, +got):", diff)
+			}
+		})
+	}
+}
+
+func TestMultiBrokerSetDefaults(t *testing.T) {
+	brokerClasses := make(map[string]*config.BrokerConfigSpec)
+	brokerSpec1 := &config.BrokerSpec{
+		Config: &duckv1.KReference{
+			Kind:       "ConfigMap",
+			APIVersion: "v1",
+			Namespace:  "knative-eventing",
+			Name:       "mt-test",
+		},
+		Delivery: &eventingduckv1.DeliverySpec{
+			DeadLetterSink: &duckv1.Destination{
+				Ref: &duckv1.KReference{
+					Kind:       "Service",
+					Namespace:  "default",
+					Name:       "mt-error",
+					APIVersion: "serving.knative.dev/v1",
+				},
+			},
+			Retry:         pointer.Int32(5),
+			BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("exponential")),
+			BackoffDelay:  pointer.String("5s"),
+		},
+	}
+	brokerConfigSpec1 := &config.BrokerConfigSpec{
+		Spec: brokerSpec1,
+	}
+	brokerSpec2 := &config.BrokerSpec{
+		Config: &duckv1.KReference{
+			Kind:       "ConfigMap",
+			APIVersion: "v1",
+			Namespace:  "knative-eventing",
+			Name:       "kafka-test",
+		},
+		Delivery: &eventingduckv1.DeliverySpec{
+			DeadLetterSink: &duckv1.Destination{
+				Ref: &duckv1.KReference{
+					Kind:       "Service",
+					Namespace:  "default",
+					Name:       "kafka-error",
+					APIVersion: "serving.knative.dev/v1",
+				},
+			},
+			Retry:         pointer.Int32(5),
+			BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("exponential")),
+			BackoffDelay:  pointer.String("5s"),
+		},
+	}
+	brokerConfigSpec2 := &config.BrokerConfigSpec{
+		Spec: brokerSpec2,
+	}
+
+	brokerSpec3 := &config.BrokerSpec{
+		Config: &duckv1.KReference{
+			Kind:       "ConfigMap",
+			APIVersion: "v1",
+			Namespace:  "knative-eventing",
+			Name:       "rabbitmq-test",
+		},
+		Delivery: nil,
+	}
+	brokerConfigSpec3 := &config.BrokerConfigSpec{
+		Spec: brokerSpec3,
+	}
+
+	brokerClasses["MTChannelBasedBroker"] = brokerConfigSpec1
+	brokerClasses["KafkaBroker"] = brokerConfigSpec2
+	brokerClasses["RabbitmqBroker"] = brokerConfigSpec3
+	defaultConfig2.Defaults.ClusterDefault.BrokerClasses = brokerClasses
+	testCases := map[string]struct {
+		initial  Broker
+		expected Broker
+	}{
+		"use config, missing namespace, defaulted": {
+			initial: Broker{
+				ObjectMeta: metav1.ObjectMeta{Namespace: "nsrandom"},
+				Spec: BrokerSpec{
+					Config: &duckv1.KReference{
+						Kind:       "ConfigMap",
+						Name:       "natss-channel",
+						APIVersion: "v1",
+					},
+					Delivery: &eventingduckv1.DeliverySpec{
+						DeadLetterSink: &duckv1.Destination{
+							Ref: &duckv1.KReference{
+								Kind:       "Service",
+								Namespace:  "rando",
+								Name:       "handle-error",
+								APIVersion: "serving.knative.dev/v1",
+							},
+						},
+						Retry:         pointer.Int32(5),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("linear")),
+						BackoffDelay:  pointer.String("5s"),
+					},
+				},
+			},
+			expected: Broker{
+				ObjectMeta: metav1.ObjectMeta{
+					Namespace: "nsrandom",
+					Annotations: map[string]string{
+						eventing.BrokerClassKey: eventing.MTChannelBrokerClassValue,
+					},
+				},
+				Spec: BrokerSpec{
+					Config: &duckv1.KReference{
+						Kind:       "ConfigMap",
+						Namespace:  "nsrandom",
+						Name:       "natss-channel",
+						APIVersion: "v1",
+					},
+					Delivery: &eventingduckv1.DeliverySpec{
+						DeadLetterSink: &duckv1.Destination{
+							Ref: &duckv1.KReference{
+								Kind:       "Service",
+								Namespace:  "rando",
+								Name:       "handle-error",
+								APIVersion: "serving.knative.dev/v1",
+							},
+						},
+						Retry:         pointer.Int32(5),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("linear")),
+						BackoffDelay:  pointer.String("5s"),
+					},
+				},
+			},
+		},
+
+		"no config, missing namespace, uses defaulted class and corresponding config": {
+			initial: Broker{
+				ObjectMeta: metav1.ObjectMeta{Namespace: "random"},
+			},
+			expected: Broker{
+				ObjectMeta: metav1.ObjectMeta{
+					Namespace: "random",
+					Annotations: map[string]string{
+						eventing.BrokerClassKey: eventing.MTChannelBrokerClassValue,
+					},
+				},
+				Spec: BrokerSpec{
+					Config: &duckv1.KReference{
+						Kind:       "ConfigMap",
+						APIVersion: "v1",
+						Namespace:  "knative-eventing",
+						Name:       "mt-test",
+					},
+					Delivery: &eventingduckv1.DeliverySpec{
+						DeadLetterSink: &duckv1.Destination{
+							Ref: &duckv1.KReference{
+								Kind:       "Service",
+								Namespace:  "default",
+								Name:       "mt-error",
+								APIVersion: "serving.knative.dev/v1",
+							},
+						},
+						Retry:         pointer.Int32(5),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("exponential")),
+						BackoffDelay:  pointer.String("5s"),
+					},
+				},
+			},
+		},
+		"no config, uses namespace broker class and config": {
+			initial: Broker{
+				ObjectMeta: metav1.ObjectMeta{Namespace: "mynamespace1"},
+			},
+			expected: Broker{
+				ObjectMeta: metav1.ObjectMeta{
+					Namespace: "mynamespace1",
+					Annotations: map[string]string{
+						eventing.BrokerClassKey: "KafkaBroker",
+					},
+				},
+				Spec: BrokerSpec{
+					Config: &duckv1.KReference{
+						APIVersion: "v1",
+						Kind:       "ConfigMap",
+						Namespace:  "knative-eventing",
+						Name:       "kafka-channel",
+					},
+					Delivery: &eventingduckv1.DeliverySpec{
+						DeadLetterSink: &duckv1.Destination{
+							Ref: &duckv1.KReference{
+								Kind:       "Service",
+								Namespace:  "default",
+								Name:       "handle-error",
+								APIVersion: "serving.knative.dev/v1",
+							},
+						},
+						Retry:         pointer.Int32(5),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("exponential")),
+						BackoffDelay:  pointer.String("5s"),
+					},
+				},
+			},
+		},
+		"no config,  uses mynamespace2's broker class and corresponding config, cluster class": {
+			initial: Broker{
+				ObjectMeta: metav1.ObjectMeta{Namespace: "mynamespace2"},
+			},
+			expected: Broker{
+				ObjectMeta: metav1.ObjectMeta{
+					Namespace: "mynamespace2",
+					Annotations: map[string]string{
+						eventing.BrokerClassKey: "RabbitmqBroker",
+					},
+				},
+				Spec: BrokerSpec{
+					Config: &duckv1.KReference{
+						Kind:       "ConfigMap",
+						APIVersion: "v1",
+						Namespace:  "knative-eventing",
+						Name:       "rabbitmq-test",
+					},
+					Delivery: nil,
+				},
+			},
+		},
+		"no config, uses mynamespace3's broker class and corresponding config, cluster class": {
+			initial: Broker{
+				ObjectMeta: metav1.ObjectMeta{Namespace: "mynamespace3"},
+			},
+			expected: Broker{
+				ObjectMeta: metav1.ObjectMeta{
+					Namespace: "mynamespace3",
+					Annotations: map[string]string{
+						eventing.BrokerClassKey: "KafkaBroker",
+					},
+				},
+				Spec: BrokerSpec{
+					Config: &duckv1.KReference{
+						Kind:       "ConfigMap",
+						APIVersion: "v1",
+						Namespace:  "knative-eventing",
+						Name:       "kafka-test",
+					},
+					Delivery: &eventingduckv1.DeliverySpec{
+						DeadLetterSink: &duckv1.Destination{
+							Ref: &duckv1.KReference{
+								Kind:       "Service",
+								Namespace:  "default",
+								Name:       "kafka-error",
+								APIVersion: "serving.knative.dev/v1",
+							},
+						},
+						Retry:         pointer.Int32(5),
+						BackoffPolicy: (*eventingduckv1.BackoffPolicyType)(pointer.String("exponential")),
+						BackoffDelay:  pointer.String("5s"),
 					},
 				},
 			},
@@ -464,7 +768,7 @@ func TestBrokerSetDefaults(t *testing.T) {
 	}
 	for n, tc := range testCases {
 		t.Run(n, func(t *testing.T) {
-			tc.initial.SetDefaults(config.ToContext(context.Background(), defaultConfig))
+			tc.initial.SetDefaults(config.ToContext(context.Background(), defaultConfig2))
 			if diff := cmp.Diff(tc.expected, tc.initial); diff != "" {
 				t.Fatal("Unexpected defaults (-want, +got):", diff)
 			}