diff --git a/lib/mongo_client.js b/lib/mongo_client.js
index 62b0b0da58..f8aaa9d589 100644
--- a/lib/mongo_client.js
+++ b/lib/mongo_client.js
@@ -194,7 +194,8 @@ function MongoClient(url, options) {
     url: url,
     options: options || {},
     promiseLibrary: null,
-    dbCache: {}
+    dbCache: {},
+    sessions: []
   };
 
   // Get the promiseLibrary
@@ -308,6 +309,14 @@ MongoClient.prototype.close = function(force, callback) {
   // Remove listeners after emit
   self.removeAllListeners('close');
 
+  // If we have sessions, we want to send a single `endSessions` command for them,
+  // and then individually clean them up.  They will be removed from the internal state
+  // when they emit their `ended` events.
+  if (this.s.sessions.length) {
+    this.topology.endSessions(this.s.sessions);
+    this.s.sessions.forEach(session => session.endSession({ skipCommand: true }));
+  }
+
   // Callback after next event loop tick
   if (typeof callback === 'function')
     return process.nextTick(function() {
@@ -481,7 +490,13 @@ MongoClient.prototype.startSession = function(options) {
     throw new MongoError('Current topology does not support sessions');
   }
 
-  return this.topology.startSession(options);
+  const session = this.topology.startSession(options);
+  session.once('ended', () => {
+    this.s.sessions = this.s.sessions.filter(s => s.equals(session));
+  });
+
+  this.s.sessions.push(session);
+  return session;
 };
 
 var mergeOptions = function(target, source, flatten) {
diff --git a/lib/topologies/topology_base.js b/lib/topologies/topology_base.js
index c0efc4f4da..96d6d3dcc1 100644
--- a/lib/topologies/topology_base.js
+++ b/lib/topologies/topology_base.js
@@ -368,6 +368,10 @@ class TopologyBase extends EventEmitter {
     return this.s.coreTopology.getServer(options);
   }
 
+  endSessions(sessions, callback) {
+    return this.s.coreTopology.endSessions(sessions, callback);
+  }
+
   /**
    * Unref all sockets
    * @method
diff --git a/package.json b/package.json
index 7fe5f3287d..79a0a06a3c 100644
--- a/package.json
+++ b/package.json
@@ -13,7 +13,7 @@
     "official"
   ],
   "dependencies": {
-    "mongodb-core": "mongodb-js/mongodb-core#8aaac8bcc7bdc02bf8bf4b03337a0af71ddc513e"
+    "mongodb-core": "mongodb-js/mongodb-core#6510d7d3d82d84cc0811a853355deaa918b96941"
   },
   "devDependencies": {
     "betterbenchmarks": "^0.1.0",
diff --git a/test/functional/sessions_tests.js b/test/functional/sessions_tests.js
new file mode 100644
index 0000000000..4b846bde70
--- /dev/null
+++ b/test/functional/sessions_tests.js
@@ -0,0 +1,48 @@
+'use strict';
+const expect = require('chai').expect,
+  mongo = require('../..'),
+  setupDatabase = require('./shared').setupDatabase;
+
+const ignoredCommands = ['ismaster'];
+const test = { commands: { started: [], succeeded: [] } };
+describe('Sessions', function() {
+  before(function() {
+    return setupDatabase(this.configuration);
+  });
+
+  afterEach(() => test.listener.uninstrument());
+  beforeEach(function() {
+    test.commands = { started: [], succeeded: [] };
+    test.listener = mongo.instrument(err => expect(err).to.be.null);
+    test.listener.on('started', event => {
+      if (ignoredCommands.indexOf(event.commandName) === -1) test.commands.started.push(event);
+    });
+
+    test.listener.on('succeeded', event => {
+      if (ignoredCommands.indexOf(event.commandName) === -1) test.commands.succeeded.push(event);
+    });
+
+    test.client = this.configuration.newClient({ w: 1 }, { poolSize: 1, auto_reconnect: false });
+    return test.client.connect();
+  });
+
+  it('should send endSessions for multiple sessions', {
+    metadata: { requires: { topology: ['single'] } },
+    test: function(done) {
+      var client = this.configuration.newClient({ w: 1 }, { poolSize: 1, auto_reconnect: false });
+      client.connect((err, client) => {
+        let sessions = [client.startSession(), client.startSession()].map(s => s.id);
+
+        client.close(err => {
+          expect(err).to.not.exist;
+          expect(test.commands.started).to.have.length(1);
+          expect(test.commands.started[0].commandName).to.equal('endSessions');
+          expect(test.commands.started[0].command.endSessions).to.include.deep.members(sessions);
+
+          expect(client.s.sessions).to.have.length(0);
+          done();
+        });
+      });
+    }
+  });
+});
diff --git a/yarn.lock b/yarn.lock
index 55645fd494..8a37756ed7 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2115,9 +2115,9 @@ mongodb-core@mongodb-js/mongodb-core#3.0.0:
     bson "~1.0.4"
     require_optional "^1.0.1"
 
-mongodb-core@mongodb-js/mongodb-core#8aaac8bcc7bdc02bf8bf4b03337a0af71ddc513e:
+mongodb-core@mongodb-js/mongodb-core#6510d7d3d82d84cc0811a853355deaa918b96941:
   version "3.0.0-beta2"
-  resolved "https://codeload.github.com/mongodb-js/mongodb-core/tar.gz/8aaac8bcc7bdc02bf8bf4b03337a0af71ddc513e"
+  resolved "https://codeload.github.com/mongodb-js/mongodb-core/tar.gz/6510d7d3d82d84cc0811a853355deaa918b96941"
   dependencies:
     bson "~1.0.4"
     require_optional "^1.0.1"