diff --git a/Libraries/Opc.Ua.PubSub/Opc.Ua.PubSub.csproj b/Libraries/Opc.Ua.PubSub/Opc.Ua.PubSub.csproj
index f6fc47dc86..a9f12be749 100644
--- a/Libraries/Opc.Ua.PubSub/Opc.Ua.PubSub.csproj
+++ b/Libraries/Opc.Ua.PubSub/Opc.Ua.PubSub.csproj
@@ -36,7 +36,7 @@
   </ItemGroup>
   
   <ItemGroup>
-    <PackageReference Include="MQTTnet" Version="3.1.1" />
+    <PackageReference Include="MQTTnet" Version="4.2.1.781" />
     <PackageReference Include="System.Net.NetworkInformation" Version="4.3.0" />
   </ItemGroup>
 
diff --git a/Libraries/Opc.Ua.PubSub/Transport/MqttClientCreator.cs b/Libraries/Opc.Ua.PubSub/Transport/MqttClientCreator.cs
index 8a9fe1ac90..64a13db41c 100644
--- a/Libraries/Opc.Ua.PubSub/Transport/MqttClientCreator.cs
+++ b/Libraries/Opc.Ua.PubSub/Transport/MqttClientCreator.cs
@@ -33,8 +33,6 @@ using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet;
 using MQTTnet.Client;
-using MQTTnet.Client.Connecting;
-using MQTTnet.Client.Options;
 
 namespace Opc.Ua.PubSub.Transport
 {
@@ -53,8 +51,8 @@ namespace Opc.Ua.PubSub.Transport
         /// <param name="topicFilter">The topics to which to subscribe</param>
         /// <returns></returns>
         internal static async Task<IMqttClient> GetMqttClientAsync(int reconnectInterval,
-                                                                   IMqttClientOptions mqttClientOptions,
-                                                                   Action<MqttApplicationMessageReceivedEventArgs> receiveMessageHandler,
+                                                                   MqttClientOptions mqttClientOptions,
+                                                                   Func<MqttApplicationMessageReceivedEventArgs, Task> receiveMessageHandler,
                                                                    StringCollection topicFilter = null)
         {
             IMqttClient mqttClient = mqttClientFactory.Value.CreateMqttClient();
@@ -62,30 +60,26 @@ namespace Opc.Ua.PubSub.Transport
             // Hook the receiveMessageHandler in case we deal with a subscriber
             if ((receiveMessageHandler != null) && (topicFilter != null))
             {
-                HashSet<string> uniqueTopics = new HashSet<string>(topicFilter.ToArray());
-                List<MqttTopicFilter> topics = new List<MqttTopicFilter>();
-                foreach (var topic in uniqueTopics)
-                {
-                    MqttTopicFilter tf = new MqttTopicFilter();
-                    tf.Topic = topic;
-                    topics.Add(tf);
-                }
 
-                mqttClient.UseApplicationMessageReceivedHandler(receiveMessageHandler);
-                mqttClient.UseConnectedHandler(async e => {
+                mqttClient.ApplicationMessageReceivedAsync += receiveMessageHandler;
+                mqttClient.ConnectedAsync += async e => {
                     Utils.Trace("{0} Connected to MQTTBroker", mqttClient?.Options?.ClientId);
 
                     try
                     {
-                        // subscribe to provided topics, messages are also filtered on the receiveMessageHandler
-                        await mqttClient.SubscribeAsync(topics.ToArray()).ConfigureAwait(false);
-                        Utils.Trace("{0} Subscribed to topics: {1}", mqttClient?.Options?.ClientId, string.Join(",", topics));
+                        foreach (string topic in topicFilter)
+                        {
+                            // subscribe to provided topics, messages are also filtered on the receiveMessageHandler
+                            await mqttClient.SubscribeAsync(topic).ConfigureAwait(false);
+                        }
+
+                        Utils.Trace("{0} Subscribed to topics: {1}", mqttClient?.Options?.ClientId, string.Join(",", topicFilter));
                     }
                     catch (Exception exception)
                     {
-                        Utils.Trace(exception, "{0} could not subscribe to topics: {1}", mqttClient?.Options?.ClientId, string.Join(",", topics));
+                        Utils.Trace(exception, "{0} could not subscribe to topics: {1}", mqttClient?.Options?.ClientId, string.Join(",", topicFilter));
                     }
-                });
+                };
             }
             else
             {
@@ -100,7 +94,7 @@ namespace Opc.Ua.PubSub.Transport
             }
 
             // Setup reconnect handler
-            mqttClient.UseDisconnectedHandler(async e => {
+            mqttClient.DisconnectedAsync += async e => {
                 await Task.Delay(TimeSpan.FromSeconds(reconnectInterval)).ConfigureAwait(false);
                 try
                 {
@@ -114,7 +108,7 @@ namespace Opc.Ua.PubSub.Transport
                 {
                     Utils.Trace("{0} Failed to reconnect after disconnect occurred: {1}", mqttClient?.Options?.ClientId, excOnDisconnect.Message);
                 }
-            });
+            };
 
             await Connect(reconnectInterval, mqttClientOptions, mqttClient).ConfigureAwait(false);
 
@@ -127,7 +121,7 @@ namespace Opc.Ua.PubSub.Transport
         /// <param name="reconnectInterval"></param>
         /// <param name="mqttClientOptions"></param>
         /// <param name="mqttClient"></param>
-        private static async Task Connect(int reconnectInterval, IMqttClientOptions mqttClientOptions, IMqttClient mqttClient)
+        private static async Task Connect(int reconnectInterval, MqttClientOptions mqttClientOptions, IMqttClient mqttClient)
         {
             try
             {
diff --git a/Libraries/Opc.Ua.PubSub/Transport/MqttPubSubConnection.cs b/Libraries/Opc.Ua.PubSub/Transport/MqttPubSubConnection.cs
index 889d78603d..845a517876 100644
--- a/Libraries/Opc.Ua.PubSub/Transport/MqttPubSubConnection.cs
+++ b/Libraries/Opc.Ua.PubSub/Transport/MqttPubSubConnection.cs
@@ -33,7 +33,6 @@ using System.Security.Cryptography.X509Certificates;
 using System.Threading.Tasks;
 using MQTTnet;
 using MQTTnet.Client;
-using MQTTnet.Client.Options;
 using MQTTnet.Formatter;
 using MQTTnet.Protocol;
 using Opc.Ua.PubSub.Encoding;
@@ -246,7 +245,7 @@ namespace Opc.Ua.PubSub.Transport
                             {
                                 var message = new MqttApplicationMessage {
                                     Topic = queueName,
-                                    Payload = bytes,
+                                    PayloadSegment = new ArraySegment<byte>(bytes),
                                     QualityOfServiceLevel = GetMqttQualityOfServiceLevel(qos),
                                     Retain = networkMessage.IsMetaDataMessage
                                 };
@@ -360,7 +359,7 @@ namespace Opc.Ua.PubSub.Transport
 
             MqttClient publisherClient = null;
             MqttClient subscriberClient = null;
-            IMqttClientOptions mqttOptions = GetMqttClientOptions();
+            MqttClientOptions mqttOptions = GetMqttClientOptions();
 
             int nrOfPublishers = Publishers.Count;
             int nrOfSubscribers = GetAllDataSetReaders().Count;
@@ -508,7 +507,7 @@ namespace Opc.Ua.PubSub.Transport
         /// Processes a message from the MQTT broker.
         /// </summary>
         /// <param name="eventArgs"></param>
-        private void ProcessMqttMessage(MqttApplicationMessageReceivedEventArgs eventArgs)
+        private Task ProcessMqttMessage(MqttApplicationMessageReceivedEventArgs eventArgs)
         {
             string topic = eventArgs.ApplicationMessage.Topic;
 
@@ -549,7 +548,7 @@ namespace Opc.Ua.PubSub.Transport
             {
                 // raise RawData received event
                 RawDataReceivedEventArgs rawDataReceivedEventArgs = new RawDataReceivedEventArgs() {
-                    Message = eventArgs.ApplicationMessage.Payload,
+                    Message = eventArgs.ApplicationMessage.PayloadSegment.Array,
                     Source = topic,
                     TransportProtocol = this.TransportProtocol,
                     MessageMapping = m_messageMapping,
@@ -563,7 +562,7 @@ namespace Opc.Ua.PubSub.Transport
                 if (rawDataReceivedEventArgs.Handled)
                 {
                     Utils.Trace("MqttConnection message from topic={0} is marked as handled and will not be decoded.", topic);
-                    return;
+                    return Task.CompletedTask;
                 }
 
                 // initialize the expected NetworkMessage
@@ -572,7 +571,7 @@ namespace Opc.Ua.PubSub.Transport
                 // trigger message decoding
                 if (networkMessage != null)
                 {
-                    networkMessage.Decode(MessageContext, eventArgs.ApplicationMessage.Payload, dataSetReaders);
+                    networkMessage.Decode(MessageContext, eventArgs.ApplicationMessage.PayloadSegment.Array, dataSetReaders);
 
                     // Handle the decoded message and raise the necessary event on UaPubSubApplication 
                     ProcessDecodedNetworkMessage(networkMessage, topic);
@@ -582,6 +581,8 @@ namespace Opc.Ua.PubSub.Transport
             {
                 Utils.Trace("MqttConnection - ProcessMqttMessage() No DataSetReader is registered for topic={0}.", topic);
             }
+
+            return Task.CompletedTask;
         }
 
         /// <summary>
@@ -608,9 +609,9 @@ namespace Opc.Ua.PubSub.Transport
         /// Get appropriate IMqttClientOptions with which to connect to the MQTTBroker
         /// </summary>
         /// <returns></returns>
-        private IMqttClientOptions GetMqttClientOptions()
+        private MqttClientOptions GetMqttClientOptions()
         {
-            IMqttClientOptions mqttOptions = null;
+            MqttClientOptions mqttOptions = null;
             TimeSpan mqttKeepAlive = TimeSpan.FromSeconds(GetWriterGroupsMaxKeepAlive() + MaxKeepAliveIncrement);
 
             NetworkAddressUrlDataType networkAddressUrlState =
@@ -762,7 +763,7 @@ namespace Opc.Ua.PubSub.Transport
         /// Validates the broker certificate.
         /// </summary>
         /// <param name="context">The context of the validation</param>
-        private bool ValidateBrokerCertificate(MqttClientCertificateValidationCallbackContext context)
+        private bool ValidateBrokerCertificate(MqttClientCertificateValidationEventArgs context)
         {
             X509Certificate2 brokerCertificate = new X509Certificate2(context.Certificate.GetRawCertData());