diff --git a/nemo_run/core/execution/slurm.py b/nemo_run/core/execution/slurm.py
index 2a794e30..139755d9 100644
--- a/nemo_run/core/execution/slurm.py
+++ b/nemo_run/core/execution/slurm.py
@@ -434,7 +434,7 @@ def info(self) -> str:
         return f"{self.__class__.__qualname__} on {self.tunnel.key}"
 
     def alloc(self, job_name="interactive"):
-        self.job_name = f"{self.job_name_prefix}{job_name}"
+        self.job_name = f"{self.job_name_prefix or ''}{job_name}"
         args = [
             f"--{arg}={getattr(self, arg.replace('-', '_'))}"
             for arg in self.ALLOC_ARGS
@@ -457,7 +457,7 @@ def srun(
         arg_dict=None,
         **kwargs,
     ):
-        self.job_name = f"{self.job_name_prefix}{job_name}"
+        self.job_name = f"{self.job_name_prefix or ''}{job_name}"
         _arg_dict = {
             arg: getattr(self, arg.replace("-", "_"))
             for arg in self.SRUN_ARGS
diff --git a/test/core/execution/test_slurm_job_name.py b/test/core/execution/test_slurm_job_name.py
new file mode 100644
index 00000000..8ce44f46
--- /dev/null
+++ b/test/core/execution/test_slurm_job_name.py
@@ -0,0 +1,75 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from unittest.mock import MagicMock, PropertyMock, patch
+
+from nemo_run.core.execution.slurm import SlurmExecutor
+from nemo_run.core.tunnel.client import LocalTunnel
+
+
+class TestSlurmJobNamePrefix:
+    def test_alloc_without_prefix_uses_job_name_only(self):
+        """alloc() must not prepend 'None' when job_name_prefix is unset."""
+        executor = SlurmExecutor(account="test", tunnel=LocalTunnel(job_dir="/tmp"))
+        assert executor.job_name_prefix is None
+
+        mock_slurm = MagicMock()
+        with patch.object(
+            SlurmExecutor, "slurm", new_callable=PropertyMock, return_value=mock_slurm
+        ):
+            executor.alloc(job_name="interactive")
+
+        assert executor.job_name == "interactive"
+
+    def test_alloc_with_prefix_prefixes_job_name(self):
+        """alloc() must prepend the configured prefix when set."""
+        executor = SlurmExecutor(
+            account="test", tunnel=LocalTunnel(job_dir="/tmp"), job_name_prefix="nemo-"
+        )
+        mock_slurm = MagicMock()
+        with patch.object(
+            SlurmExecutor, "slurm", new_callable=PropertyMock, return_value=mock_slurm
+        ):
+            executor.alloc(job_name="interactive")
+
+        assert executor.job_name == "nemo-interactive"
+
+    def test_srun_without_prefix_uses_job_name_only(self):
+        """srun() must not prepend 'None' when job_name_prefix is unset."""
+        executor = SlurmExecutor(account="test", tunnel=LocalTunnel(job_dir="/tmp"))
+        assert executor.job_name_prefix is None
+
+        mock_slurm = MagicMock()
+        with patch.object(
+            SlurmExecutor, "slurm", new_callable=PropertyMock, return_value=mock_slurm
+        ):
+            with patch.object(executor, "SRUN_ARGS", []):
+                executor.srun("echo hi", job_name="interactive")
+
+        assert executor.job_name == "interactive"
+
+    def test_srun_with_prefix_prefixes_job_name(self):
+        """srun() must prepend the configured prefix when set."""
+        executor = SlurmExecutor(
+            account="test", tunnel=LocalTunnel(job_dir="/tmp"), job_name_prefix="nemo-"
+        )
+        mock_slurm = MagicMock()
+        with patch.object(
+            SlurmExecutor, "slurm", new_callable=PropertyMock, return_value=mock_slurm
+        ):
+            with patch.object(executor, "SRUN_ARGS", []):
+                executor.srun("echo hi", job_name="interactive")
+
+        assert executor.job_name == "nemo-interactive"