diff --git a/tools/projmgr/include/ProjMgrRunDebug.h b/tools/projmgr/include/ProjMgrRunDebug.h
index e4bf6c1db..ccacc5997 100644
--- a/tools/projmgr/include/ProjMgrRunDebug.h
+++ b/tools/projmgr/include/ProjMgrRunDebug.h
@@ -227,6 +227,7 @@ class ProjMgrRunDebug {
     const std::map<std::string, RteDeviceProperty*>& pnames);
   void CollectTelnetOptions(const ContextItem& context, DebugAdapterItem& adapter,
     const std::map<std::string, RteDeviceProperty*>& pnames);
+  void SetTelnetPort(TelnetOptionsItem& item, unsigned long long& port, std::set<unsigned long long>& usedPorts);
   CustomItem& CustomMapFind(std::vector<std::pair<std::string, CustomItem>>& customMap, const std::string& key);
   void MergeCustomItems(const CustomItem& src, CustomItem& dst);
 };
diff --git a/tools/projmgr/src/ProjMgrRunDebug.cpp b/tools/projmgr/src/ProjMgrRunDebug.cpp
index 33920d5b5..7411927cb 100644
--- a/tools/projmgr/src/ProjMgrRunDebug.cpp
+++ b/tools/projmgr/src/ProjMgrRunDebug.cpp
@@ -410,29 +410,34 @@ void ProjMgrRunDebug::CollectTelnetOptions(const ContextItem& context, DebugAdap
     unsigned long long port = adapter.defaults.telnet.port.empty() ? 0 : RteUtils::StringToULL(adapter.defaults.telnet.port);
     if (m_runDebug.debugger.telnet.find(m_runDebug.debugger.startPname) != m_runDebug.debugger.telnet.end()) {
       // add primary processor port first
-      auto& startPort = m_runDebug.debugger.telnet[m_runDebug.debugger.startPname].ullPort;
-      if (startPort == 0) {
-        startPort = port;
-      } else {
-        port = startPort;
-      }
-      usedPorts.insert(port);
+      auto& start = m_runDebug.debugger.telnet[m_runDebug.debugger.startPname];
+      // set next available port
+      SetTelnetPort(start, port, usedPorts);
+      // set starting port for other processors
+      port = start.ullPort;
     }
     for (auto& [pname, telnet] : m_runDebug.debugger.telnet) {
       // add ports for other processors
       if (pname != m_runDebug.debugger.startPname) {
-        // get customized port if set
-        port = telnet.port.empty() ? port : telnet.ullPort;
-        while (usedPorts.find(port) != usedPorts.end()) {
-          // skip port number if it has already been used
-          port++;
-        }
-        telnet.ullPort = port;
+        // set next available port
+        SetTelnetPort(telnet, port, usedPorts);
       }
     }
   }
 }
 
+void ProjMgrRunDebug::SetTelnetPort(TelnetOptionsItem& item, unsigned long long& port, std::set<unsigned long long>& usedPorts) {
+  // only assign a port number if it has not been already specified
+  if (item.port.empty()) {
+    while (usedPorts.find(port) != usedPorts.end()) {
+      // skip port number if it has already been used
+      port++;
+    }
+    item.ullPort = port;
+    usedPorts.insert(port);
+  }
+}
+
 void ProjMgrRunDebug::CollectDebugTopology(const ContextItem& context, const vector<pair<const RteItem*, vector<string>>> debugs,
   const std::map<std::string, RteDeviceProperty*>& pnames) {
   // debug topology
diff --git a/tools/projmgr/test/data/TestRunDebug/telnet.csolution.yml b/tools/projmgr/test/data/TestRunDebug/telnet.csolution.yml
index e142db8a2..9f3ff9a40 100644
--- a/tools/projmgr/test/data/TestRunDebug/telnet.csolution.yml
+++ b/tools/projmgr/test/data/TestRunDebug/telnet.csolution.yml
@@ -54,6 +54,20 @@ solution:
             name: J-Link Server
             start-pname: cm0_core1
 
+        - set: CustomPorts
+          images:
+            - project-context: core0
+            - project-context: core1
+          debugger:
+            name: CMSIS-DAP
+            telnet:
+              - mode: monitor
+                pname: cm0_core1
+                port: 1234
+              - mode: monitor
+                pname: cm0_core0
+                port: 5678
+
         - set: Warnings
           images:
             - project-context: core0
diff --git a/tools/projmgr/test/src/ProjMgrUnitTests.cpp b/tools/projmgr/test/src/ProjMgrUnitTests.cpp
index 16e25e55a..769fb7987 100644
--- a/tools/projmgr/test/src/ProjMgrUnitTests.cpp
+++ b/tools/projmgr/test/src/ProjMgrUnitTests.cpp
@@ -6904,6 +6904,20 @@ R"(- mode: off
   pname: cm0_core1
   port: 4444)", sstream3.str());
 
+  // dual core with custom port numbers
+  argv[6] = (char*)"DualCore@CustomPorts";
+  EXPECT_EQ(0, RunProjMgr(7, argv, m_envp));
+  const YAML::Node& cbuildrun4 = YAML::LoadFile(testoutput_folder + "/out/telnet+DualCore.cbuild-run.yml");
+  stringstream sstream4;
+  sstream4 << cbuildrun4["cbuild-run"]["debugger"]["telnet"];
+  EXPECT_EQ(
+    R"(- mode: monitor
+  pname: cm0_core0
+  port: 5678
+- mode: monitor
+  pname: cm0_core1
+  port: 1234)", sstream4.str());
+
   // warnings
   StdStreamRedirect streamRedirect;
   argv[6] = (char*)"DualCore@Warnings";