diff --git a/changelogs/fragments/58039-docker_swarm_service-fix-resource-lookup.yaml b/changelogs/fragments/58039-docker_swarm_service-fix-resource-lookup.yaml
new file mode 100644
index 0000000000..63daa74a74
--- /dev/null
+++ b/changelogs/fragments/58039-docker_swarm_service-fix-resource-lookup.yaml
@@ -0,0 +1,2 @@
+bugfixes:
+  - docker_swarm_service - fix resource lookup if mounts.source="".
diff --git a/lib/ansible/modules/cloud/docker/docker_swarm_service.py b/lib/ansible/modules/cloud/docker/docker_swarm_service.py
index 296420a5e6..96cc5f8aa1 100644
--- a/lib/ansible/modules/cloud/docker/docker_swarm_service.py
+++ b/lib/ansible/modules/cloud/docker/docker_swarm_service.py
@@ -2230,7 +2230,7 @@ class DockerServiceManager(object):
                     (key.lower(), value) for key, value in driver_config.items()
                 ) or None
                 ds.mounts.append({
-                    'source': mount_data['Source'],
+                    'source': mount_data.get('Source', ''),
                     'type': mount_data['Type'],
                     'target': mount_data['Target'],
                     'readonly': mount_data.get('ReadOnly'),
diff --git a/test/integration/targets/docker_swarm_service/tasks/tests/mounts.yml b/test/integration/targets/docker_swarm_service/tasks/tests/mounts.yml
index e2c2029329..5063648e61 100644
--- a/test/integration/targets/docker_swarm_service/tasks/tests/mounts.yml
+++ b/test/integration/targets/docker_swarm_service/tasks/tests/mounts.yml
@@ -509,6 +509,53 @@
     - "'Minimum version required' in mounts_tmpfs_size_1.msg"
   when: docker_py_version is version('2.6.0', '<')
 
+####################################################################
+## mounts.source ###################################################
+####################################################################
+
+- name: mounts.source (empty for tmpfs)
+  docker_swarm_service:
+    name: "{{ service_name }}"
+    image: alpine:3.8
+    resolve_image: no
+    command: '/bin/sh -v -c "sleep 10m"'
+    mounts:
+      - source: ""
+        target: "/tmp/{{ volume_name_1 }}"
+        type: "tmpfs"
+  register: mounts_tmpfs_source_1
+  ignore_errors: yes
+
+- name: mounts.source (empty for tmpfs idempotency)
+  docker_swarm_service:
+    name: "{{ service_name }}"
+    image: alpine:3.8
+    resolve_image: no
+    command: '/bin/sh -v -c "sleep 10m"'
+    mounts:
+      - source: ""
+        target: "/tmp/{{ volume_name_1 }}"
+        type: "tmpfs"
+  register: mounts_tmpfs_source_2
+  ignore_errors: yes
+
+- name: cleanup
+  docker_swarm_service:
+    name: "{{ service_name }}"
+    state: absent
+  diff: no
+
+- assert:
+    that:
+      - mounts_tmpfs_source_1 is changed
+      - mounts_tmpfs_source_2 is not changed
+  when: docker_py_version is version('2.6.0', '>=')
+- assert:
+    that:
+    - mounts_tmpfs_source_1 is failed
+    - "'Minimum version required' in mounts_tmpfs_source_1.msg"
+  when: docker_py_version is version('2.6.0', '<')
+
 ####################################################################
 ####################################################################
 ####################################################################