diff --git a/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/SubscriptionManager.java b/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/SubscriptionManager.java
index 40a273fc6c..12d4fa277a 100644
--- a/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/SubscriptionManager.java
+++ b/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/SubscriptionManager.java
@@ -70,17 +70,26 @@ public class SubscriptionManager extends AbstractVerticle {
   }
 
   public boolean unsubscribe(final UnsubscribeRequest request) {
-    LOG.debug("Unsubscribe request subscriptionId = {}", request.getSubscriptionId());
+    final Long subscriptionId = request.getSubscriptionId();
+    final String connectionId = request.getConnectionId();
 
-    if (!subscriptions.containsKey(request.getSubscriptionId())) {
-      throw new SubscriptionNotFoundException(request.getSubscriptionId());
+    LOG.debug("Unsubscribe request subscriptionId = {}", subscriptionId);
+
+    if (!subscriptions.containsKey(subscriptionId)
+        || !connectionOwnsSubscription(subscriptionId, connectionId)) {
+      throw new SubscriptionNotFoundException(subscriptionId);
     }
 
-    destroySubscription(request.getSubscriptionId(), request.getConnectionId());
+    destroySubscription(subscriptionId, connectionId);
 
     return true;
   }
 
+  private boolean connectionOwnsSubscription(final Long subscriptionId, final String connectionId) {
+    return connectionSubscriptionsMap.get(connectionId) != null
+        && connectionSubscriptionsMap.get(connectionId).contains(subscriptionId);
+  }
+
   private void destroySubscription(final long subscriptionId, final String connectionId) {
     subscriptions.remove(subscriptionId);
 
diff --git a/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/SubscriptionManagerTest.java b/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/SubscriptionManagerTest.java
index 9be74b7b47..227636af83 100644
--- a/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/SubscriptionManagerTest.java
+++ b/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/SubscriptionManagerTest.java
@@ -1,6 +1,7 @@
 package tech.pegasys.pantheon.ethereum.jsonrpc.websocket.subscription;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.catchThrowable;
 import static org.hamcrest.CoreMatchers.both;
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.CoreMatchers.instanceOf;
@@ -13,6 +14,7 @@ import tech.pegasys.pantheon.ethereum.jsonrpc.websocket.subscription.request.Uns
 import tech.pegasys.pantheon.ethereum.jsonrpc.websocket.subscription.syncing.SyncingSubscription;
 
 import java.util.List;
+import java.util.UUID;
 
 import org.junit.Before;
 import org.junit.Rule;
@@ -33,8 +35,7 @@ public class SubscriptionManagerTest {
 
   @Test
   public void subscribeShouldCreateSubscription() {
-    final SubscribeRequest subscribeRequest =
-        new SubscribeRequest(SubscriptionType.SYNCING, null, null, CONNECTION_ID);
+    final SubscribeRequest subscribeRequest = subscribeRequest(CONNECTION_ID);
 
     final Long subscriptionId = subscriptionManager.subscribe(subscribeRequest);
 
@@ -49,8 +50,7 @@ public class SubscriptionManagerTest {
 
   @Test
   public void unsubscribeExistingSubscriptionShouldDestroySubscription() {
-    final SubscribeRequest subscribeRequest =
-        new SubscribeRequest(SubscriptionType.SYNCING, null, null, CONNECTION_ID);
+    final SubscribeRequest subscribeRequest = subscribeRequest(CONNECTION_ID);
     final Long subscriptionId = subscriptionManager.subscribe(subscribeRequest);
 
     assertThat(subscriptionManager.subscriptions().get(subscriptionId)).isNotNull();
@@ -76,8 +76,7 @@ public class SubscriptionManagerTest {
 
   @Test
   public void shouldAddSubscriptionToNewConnection() {
-    final SubscribeRequest subscribeRequest =
-        new SubscribeRequest(SubscriptionType.SYNCING, null, null, CONNECTION_ID);
+    final SubscribeRequest subscribeRequest = subscribeRequest(CONNECTION_ID);
 
     subscriptionManager.subscribe(subscribeRequest);
 
@@ -90,8 +89,7 @@ public class SubscriptionManagerTest {
 
   @Test
   public void shouldAddSubscriptionToExistingConnection() {
-    final SubscribeRequest subscribeRequest =
-        new SubscribeRequest(SubscriptionType.SYNCING, null, null, CONNECTION_ID);
+    final SubscribeRequest subscribeRequest = subscribeRequest(CONNECTION_ID);
 
     subscriptionManager.subscribe(subscribeRequest);
 
@@ -110,8 +108,7 @@ public class SubscriptionManagerTest {
 
   @Test
   public void shouldRemoveSubscriptionFromExistingConnection() {
-    final SubscribeRequest subscribeRequest =
-        new SubscribeRequest(SubscriptionType.SYNCING, null, null, CONNECTION_ID);
+    final SubscribeRequest subscribeRequest = subscribeRequest(CONNECTION_ID);
 
     final Long subscriptionId1 = subscriptionManager.subscribe(subscribeRequest);
 
@@ -140,8 +137,7 @@ public class SubscriptionManagerTest {
 
   @Test
   public void shouldRemoveConnectionWithSingleSubscriptions() {
-    final SubscribeRequest subscribeRequest =
-        new SubscribeRequest(SubscriptionType.SYNCING, null, null, CONNECTION_ID);
+    final SubscribeRequest subscribeRequest = subscribeRequest(CONNECTION_ID);
 
     final Long subscriptionId1 = subscriptionManager.subscribe(subscribeRequest);
 
@@ -188,17 +184,37 @@ public class SubscriptionManagerTest {
   }
 
   @Test
-  public void unsubscribeWithUnknownConnectionId() {
-    final SubscribeRequest subscribeRequestOne =
-        new SubscribeRequest(SubscriptionType.NEW_BLOCK_HEADERS, null, true, CONNECTION_ID);
-    final long subscriptionId = subscriptionManager.subscribe(subscribeRequestOne);
+  public void unsubscribeOthersSubscriptionsNotHavingOwnSubscriptionShouldReturnNotFound() {
+    SubscribeRequest subscribeRequest = subscribeRequest(CONNECTION_ID);
+    Long subscriptionId = subscriptionManager.subscribe(subscribeRequest);
 
-    final boolean success =
-        subscriptionManager.unsubscribe(
-            new UnsubscribeRequest(subscriptionId, "unknown-connection-id"));
+    UnsubscribeRequest unsubscribeRequest =
+        new UnsubscribeRequest(subscriptionId, UUID.randomUUID().toString());
 
-    assertThat(success).isTrue();
+    final Throwable thrown =
+        catchThrowable(() -> subscriptionManager.unsubscribe(unsubscribeRequest));
+    assertThat(thrown).isInstanceOf(SubscriptionNotFoundException.class);
   }
 
-  // TODO vertx event bus testing for response
+  @Test
+  public void unsubscribeOthersSubscriptionsHavingOwnSubscriptionShouldReturnNotFound() {
+    String ownConnectionId = UUID.randomUUID().toString();
+    SubscribeRequest ownSubscribeRequest = subscribeRequest(ownConnectionId);
+    subscriptionManager.subscribe(ownSubscribeRequest);
+
+    String otherConnectionId = UUID.randomUUID().toString();
+    SubscribeRequest otherSubscribeRequest = subscribeRequest(otherConnectionId);
+    Long otherSubscriptionId = subscriptionManager.subscribe(otherSubscribeRequest);
+
+    UnsubscribeRequest unsubscribeRequest =
+        new UnsubscribeRequest(otherSubscriptionId, ownConnectionId);
+
+    final Throwable thrown =
+        catchThrowable(() -> subscriptionManager.unsubscribe(unsubscribeRequest));
+    assertThat(thrown).isInstanceOf(SubscriptionNotFoundException.class);
+  }
+
+  private SubscribeRequest subscribeRequest(final String connectionId) {
+    return new SubscribeRequest(SubscriptionType.SYNCING, null, null, connectionId);
+  }
 }