diff --git a/rllib/evaluation/rollout_worker.py b/rllib/evaluation/rollout_worker.py
index 96982de20e7e..18a9ff5da6f2 100644
--- a/rllib/evaluation/rollout_worker.py
+++ b/rllib/evaluation/rollout_worker.py
@@ -74,6 +74,72 @@ def get_global_worker() -> "RolloutWorker":
     return _global_worker
 
 
+def _update_global_seed(policy_config: TrainerConfigDict, seed: int):
+    """Set Python random, numpy, env, and torch/tf seeds.
+
+    This is useful for debugging and testing purposes.
+    """
+    if not seed:
+        return
+
+    # Python random module.
+    random.seed(seed)
+    # Numpy.
+    np.random.seed(seed)
+
+    # Torch.
+    if torch and policy_config.get("framework") == "torch":
+        torch.manual_seed(seed)
+        # See https://github.com/pytorch/pytorch/issues/47672.
+        cuda_version = torch.version.cuda
+        if cuda_version is not None and float(torch.version.cuda) >= 10.2:
+            os.environ["CUBLAS_WORKSPACE_CONFIG"] = "4096:8"
+        else:
+            from distutils.version import LooseVersion
+
+            if LooseVersion(torch.__version__) >= LooseVersion("1.8.0"):
+                # Not all Operations support this.
+                torch.use_deterministic_algorithms(True)
+            else:
+                torch.set_deterministic(True)
+        # This is only for Convolution no problem.
+        torch.backends.cudnn.deterministic = True
+    # Tf2.x.
+    elif tf and policy_config.get("framework") == "tf2":
+        tf.random.set_seed(seed)
+    # Tf-eager.
+    elif tf1 and policy_config.get("framework") == "tfe":
+        tf1.set_random_seed(seed)
+
+
+def _update_env_seed(env: EnvType, seed: int, worker_idx: int,
+                     vector_idx: int):
+    """Set a deterministic random seed on environment.
+
+    TODO: does remote envs have seed() func?
+    TODO: if a gym env is wrapped in a gym.wrappers.Monitor,
+        is there still seed() func?
+    """
+    if not seed:
+        return
+
+    # A single RL job is unlikely to have more than 10K
+    # rollout workers.
+    max_num_envs_per_workers: int = 1000
+    assert worker_idx < max_num_envs_per_workers, \
+        "Too many envs per worker. Random seeds may collide."
+    computed_seed: int = (
+        worker_idx * max_num_envs_per_workers + vector_idx + seed)
+
+    # Gym.env.
+    # This will silently fail for most OpenAI gyms
+    # (they do nothing and return None per default)
+    if not hasattr(env, "seed"):
+        logger.info("Env doesn't support env.seed(): {}".format(env))
+    else:
+        env.seed(computed_seed)
+
+
 @DeveloperAPI
 class RolloutWorker(ParallelIteratorWorker):
     """Common experience collection class.
@@ -306,6 +372,7 @@ class to use.
                 gym.spaces.Space]]]): An optional space dict mapping policy IDs
                 to (obs_space, action_space)-tuples. This is used in case no
                 Env is created on this RolloutWorker.
+            policy: Obsoleted arg. Use `policy_spec` instead.
             monitor_path: Obsoleted arg. Use `record_env` instead.
         """
 
@@ -394,6 +461,8 @@ def gen_rollouts():
 
         self.env = None
 
+        _update_global_seed(policy_config, seed)
+
         # Create an env for this worker.
         if not (worker_index == 0 and num_workers > 0
                 and not policy_config.get("create_env_on_driver")):
@@ -480,14 +549,25 @@ def wrap(env):
 
             # Wrap env through the correct wrapper.
             self.env: EnvType = wrap(self.env)
+            # Ideally, we would use the same make_env() function below
+            # to create self.env, but wrap(env) and self.env has a cyclic
+            # dependency on each other right now, so we would settle on
+            # duplicating the random seed setting logic for now.
+            _update_env_seed(self.env, seed, worker_index, 0)
 
         def make_env(vector_index):
-            return wrap(
+            env = wrap(
                 env_creator(
                     env_context.copy_with_overrides(
                         worker_index=worker_index,
                         vector_index=vector_index,
                         remote=remote_worker_envs)))
+            # make_env() is used to created additional environments
+            # during environment vectorization below.
+            # So we make sure a deterministic random seed is set on
+            # all the environments if specified.
+            _update_env_seed(env, seed, worker_index, vector_index)
+            return env
 
         self.make_env_fn = make_env
         self.spaces = spaces
@@ -507,46 +587,6 @@ def make_env(vector_index):
         self.policy_map: PolicyMap = None
         self.preprocessors: Dict[PolicyID, Preprocessor] = None
 
-        # Set Python random, numpy, env, and torch/tf seeds.
-        if seed is not None:
-            # Python random module.
-            random.seed(seed)
-            # Numpy.
-            np.random.seed(seed)
-            # Gym.env.
-            # This will silently fail for most OpenAI gyms
-            # (they do nothing and return None per default)
-            if not hasattr(self.env, "seed"):
-                logger.info("Env doesn't support env.seed(): {}".format(
-                    self.env))
-            else:
-                self.env.seed(seed)
-
-            # Torch.
-            if torch and policy_config.get("framework") == "torch":
-                torch.manual_seed(seed)
-                # See https://github.com/pytorch/pytorch/issues/47672.
-                cuda_version = torch.version.cuda
-                if cuda_version is not None and float(
-                        torch.version.cuda) >= 10.2:
-                    os.environ["CUBLAS_WORKSPACE_CONFIG"] = "4096:8"
-                else:
-                    from distutils.version import LooseVersion
-                    if LooseVersion(
-                            torch.__version__) >= LooseVersion("1.8.0"):
-                        # Not all Operations support this.
-                        torch.use_deterministic_algorithms(True)
-                    else:
-                        torch.set_deterministic(True)
-                # This is only for Convolution no problem.
-                torch.backends.cudnn.deterministic = True
-            # Tf2.x.
-            elif tf and policy_config.get("framework") == "tf2":
-                tf.random.set_seed(seed)
-            # Tf-eager.
-            elif tf1 and policy_config.get("framework") == "tfe":
-                tf1.set_random_seed(seed)
-
         # Check available number of GPUs.
         num_gpus = policy_config.get("num_gpus", 0) if \
             self.worker_index == 0 else \
diff --git a/rllib/evaluation/tests/test_rollout_worker.py b/rllib/evaluation/tests/test_rollout_worker.py
index 2ff5a5738efd..913fce2fe632 100644
--- a/rllib/evaluation/tests/test_rollout_worker.py
+++ b/rllib/evaluation/tests/test_rollout_worker.py
@@ -670,6 +670,17 @@ def test_no_env_seed(self):
         assert not hasattr(ev.env, "seed")
         ev.stop()
 
+    def test_multi_env_seed(self):
+        ev = RolloutWorker(
+            env_creator=lambda _: MockEnv2(100),
+            num_envs=3,
+            policy_spec=MockPolicy,
+            seed=1)
+        seeds = ev.foreach_env(lambda env: env.rng_seed)
+        # Make sure all environments get a different deterministic seed.
+        assert seeds == [1, 2, 3]
+        ev.stop()
+
     def sample_and_flush(self, ev):
         time.sleep(2)
         ev.sample()
diff --git a/rllib/examples/deterministic_training.py b/rllib/examples/deterministic_training.py
index c9951ae605f5..5d568c398eba 100644
--- a/rllib/examples/deterministic_training.py
+++ b/rllib/examples/deterministic_training.py
@@ -37,6 +37,8 @@
         # Use GPUs iff `RLLIB_NUM_GPUS` env var set to > 0.
         "num_gpus": int(os.environ.get("RLLIB_NUM_GPUS", "0")),
         "num_workers": 2,  # parallelism
+        # Make sure every environment gets a fixed seed.
+        "num_envs_per_worker": 2,
         "framework": args.framework,
         "seed": args.seed,
 
diff --git a/rllib/examples/env/env_using_remote_actor.py b/rllib/examples/env/env_using_remote_actor.py
index 15c5c4f610ec..1504b36cdb15 100644
--- a/rllib/examples/env/env_using_remote_actor.py
+++ b/rllib/examples/env/env_using_remote_actor.py
@@ -27,12 +27,17 @@ def __init__(self, env_config):
         # Get our param server (remote actor) by name.
         self._handler = ray.get_actor(
             env_config.get("param_server", "param-server"))
+        self.rng_seed = None
 
-    # def seed(self, seed=None):
-    #     print(f"Seeding env (worker={self.env_config.worker_index}) "
-    #           f"with {seed}")
-    #     self.np_random, seed = seeding.np_random(seed)
-    #     return [seed]
+    def seed(self, rng_seed: int = None):
+        if not rng_seed:
+            return
+
+        print(f"Seeding env (worker={self.env_config.worker_index}) "
+              f"with {rng_seed}")
+
+        self.rng_seed = rng_seed
+        self.np_random, _ = seeding.np_random(rng_seed)
 
     def reset(self):
         # Pass in our RNG to guarantee no race conditions.
@@ -43,7 +48,10 @@ def reset(self):
         # IMPORTANT: Advance the state of our RNG (self._rng was passed
         # above via ray (serialized) and thus not altered locally here!).
         # Or create a new RNG from another random number:
-        new_seed = self.np_random.randint(0, 1000000)
+        # Seed the RNG with a deterministic seed if set, otherwise, create
+        # a random one.
+        new_seed = (self.np_random.randint(0, 1000000)
+                    if not self.rng_seed else self.rng_seed)
         self.np_random, _ = seeding.np_random(new_seed)
 
         print(f"Env worker-idx={self.env_config.worker_index} "
diff --git a/rllib/examples/env/mock_env.py b/rllib/examples/env/mock_env.py
index fe58ff260c12..177f6523ac2e 100644
--- a/rllib/examples/env/mock_env.py
+++ b/rllib/examples/env/mock_env.py
@@ -39,6 +39,7 @@ def __init__(self, episode_length):
         self.i = 0
         self.observation_space = gym.spaces.Discrete(100)
         self.action_space = gym.spaces.Discrete(2)
+        self.rng_seed = None
 
     def reset(self):
         self.i = 0
@@ -48,6 +49,9 @@ def step(self, action):
         self.i += 1
         return self.i, 100.0, self.i >= self.episode_length, {}
 
+    def seed(self, rng_seed):
+        self.rng_seed = rng_seed
+
 
 class VectorizedMockEnv(VectorEnv):
     """Vectorized version of the MockEnv.