diff --git a/include/Context.h b/include/Context.h
index a284e01..0045929 100644
--- a/include/Context.h
+++ b/include/Context.h
@@ -9,6 +9,7 @@ struct Context {
     std::string topic;
     std::string message;
     std::string address;
+    std::string clientId;
     bool verbose;
 };
 
@@ -23,15 +24,16 @@ struct ParseResult {
 ParseResult parseContext(int argc, char *argv[]) noexcept;
 
 const std::string USAGE = R"(
-Usage: mqtt pub [-v] -t <topic> -a <address> <message>
+Usage: mqtt pub [-v] -t <topic> -a <address> -c <clientId> <message>
 Options:
-  -t, --topic <topic>      Specify the topic to publish to (required)
-  -a, --address <address>  <host>[:<port>] address to connect to (required)
-  -v, --verbose            Enable verbose output
-  -h, --help               Show this help message
+  -t, --topic <topic>           Specify the topic to publish to (required)
+  -a, --address <address>       <host>[:<port>] address to connect to (required)
+  -c, --client-id <client id>   Client identifier
+  -v, --verbose                 Enable verbose output
+  -h, --help                    Show this help message
 
 Example:
-  mqtt pub -t hello/topic -v -a 127.0.0.1:8883 '{"hello": "world"}'
+  mqtt pub -t hello/topic -v -a 127.0.0.1:8883 -c myclient '{"hello": "world"}'
 )";
 
 }; // namespace MqttClient
\ No newline at end of file
diff --git a/src/Context.cpp b/src/Context.cpp
index 8bc27c1..a5baf45 100644
--- a/src/Context.cpp
+++ b/src/Context.cpp
@@ -14,12 +14,13 @@ ParseResult parseContext(int argc, char *argv[]) noexcept {
 
     struct option opts[] = {{"topic", required_argument, 0, 't'},
                             {"address", required_argument, 0, 'a'},
+                            {"client-id", required_argument, 0, 'c'},
                             {"verbose", no_argument, 0, 'v'},
                             {"help", no_argument, 0, 'h'},
                             {0, 0, 0, 0}};
     int opt;
     int optInd = 0;
-    while ((opt = getopt_long(argc, argv, "t:a:vh", opts, &optInd)) != -1) {
+    while ((opt = getopt_long(argc, argv, "t:a:c:vh", opts, &optInd)) != -1) {
         switch (opt) {
         case 't':
             context.topic = optarg;
@@ -27,6 +28,9 @@ ParseResult parseContext(int argc, char *argv[]) noexcept {
         case 'a':
             context.address = optarg;
             break;
+        case 'c':
+            context.clientId = optarg;
+            break;
         case 'v':
             context.verbose = true;
             break;
@@ -54,6 +58,11 @@ ParseResult parseContext(int argc, char *argv[]) noexcept {
         return {ParseResultCode::FAILURE, "Error: Address is required"};
     }
 
+    if (context.clientId.empty()) {
+        // TODO more validations
+        return {ParseResultCode::FAILURE, "Error: Client id is required"};
+    }
+
     auto numMessages = argc - 1 - optind;
     if (numMessages == 0) {
         return {ParseResultCode::FAILURE, "Error: Message is required"};
diff --git a/src/main.cpp b/src/main.cpp
index e5296f1..5839e08 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -26,6 +26,7 @@ int main(int argc, char *argv[]) {
         std::cout << "Context[command=" << context.command
                   << ", topic=" << context.topic
                   << ", address=" << context.address
+                  << ", clientId=" << context.clientId
                   << ", message=" << context.message << "]\n";
     }
 
diff --git a/test/ContextTest.cpp b/test/ContextTest.cpp
index d5bd598..7d686ed 100644
--- a/test/ContextTest.cpp
+++ b/test/ContextTest.cpp
@@ -22,13 +22,13 @@ class ContextTest : public testing::Test {
 
 TEST_F(ContextTest, AllOpts) {
     auto res = parse({"mqtt", "pub", "-v", "-t", "topic", "-a",
-                      "127.0.0.1:8883", "message"});
+                      "127.0.0.1:8883", "-c", "client", "message"});
     EXPECT_EQ(ParseResultCode::SUCCESS, res.code);
 }
 
 TEST_F(ContextTest, RequiredOpts) {
-    auto res = parse(
-        {"mqtt", "pub", "-t", "topic", "-a", "127.0.0.1:8883", "message"});
+    auto res = parse({"mqtt", "pub", "-t", "topic", "-a", "127.0.0.1:8883",
+                      "-c", "client", "message"});
     EXPECT_EQ(ParseResultCode::SUCCESS, res.code);
 }
 
@@ -43,32 +43,48 @@ TEST_F(ContextTest, NoArgs) {
 }
 
 TEST_F(ContextTest, MissingMessage) {
-    auto res = parse({"mqtt", "pub", "-t", "topic", "-a", "127.0.0.1:8883"});
+    auto res = parse(
+        {"mqtt", "pub", "-t", "topic", "-a", "127.0.0.1:8883", "-c", "client"});
     EXPECT_EQ(ParseResultCode::FAILURE, res.code);
 }
 
 TEST_F(ContextTest, MissingTopic) {
-    auto res = parse({"mqtt", "pub", "-a", "127.0.0.1:8883", "message"});
+    auto res = parse(
+        {"mqtt", "pub", "-a", "127.0.0.1:8883", "-c", "client", "message"});
     EXPECT_EQ(ParseResultCode::FAILURE, res.code);
 }
 
 TEST_F(ContextTest, MissingTopicValue) {
-    auto res = parse({"mqtt", "pub", "-t", "-a", "127.0.0.1:8883", "message"});
+    auto res = parse({"mqtt", "pub", "-t", "-a", "127.0.0.1:8883", "-c",
+                      "client", "message"});
     EXPECT_EQ(ParseResultCode::FAILURE, res.code);
 }
 
 TEST_F(ContextTest, MissingAddress) {
-    auto res = parse({"mqtt", "pub", "-t", "topic", "message"});
+    auto res = parse({"mqtt", "pub", "-t", "topic", "-c", "client", "message"});
     EXPECT_EQ(ParseResultCode::FAILURE, res.code);
 }
 
 TEST_F(ContextTest, MissingAddressValue) {
-    auto res = parse({"mqtt", "pub", "-t", "topic", "-a", "message"});
+    auto res =
+        parse({"mqtt", "pub", "-t", "topic", "-a", "-c", "client", "message"});
     EXPECT_EQ(ParseResultCode::FAILURE, res.code);
 }
 
 TEST_F(ContextTest, MultipleMessages) {
     auto res = parse({"mqtt", "pub", "-v", "-t", "topic", "-a",
-                      "127.0.0.1:8883", "message", "message2"});
+                      "127.0.0.1:8883", "-c", "client", "message", "message2"});
+    EXPECT_EQ(ParseResultCode::FAILURE, res.code);
+}
+
+TEST_F(ContextTest, MissingClientId) {
+    auto res = parse({"mqtt", "pub", "-v", "-t", "topic", "-a",
+                      "127.0.0.1:8883", "message"});
+    EXPECT_EQ(ParseResultCode::FAILURE, res.code);
+}
+
+TEST_F(ContextTest, MissingClientIdValue) {
+    auto res = parse({"mqtt", "pub", "-v", "-t", "topic", "-a",
+                      "127.0.0.1:8883", "-c", "message"});
     EXPECT_EQ(ParseResultCode::FAILURE, res.code);
 }