diff --git a/changelogs/fragments/343-secret-check-mode.yaml b/changelogs/fragments/343-secret-check-mode.yaml
new file mode 100644
index 00000000..6351a888
--- /dev/null
+++ b/changelogs/fragments/343-secret-check-mode.yaml
@@ -0,0 +1,2 @@
+bugfixes:
+  - k8s - fix check_mode always showing changes when using stringData on Secrets (https://github.com/ansible-collections/community.kubernetes/issues/282).
diff --git a/molecule/default/tasks/apply.yml b/molecule/default/tasks/apply.yml
index 2f579755..291a35d6 100644
--- a/molecule/default/tasks/apply.yml
+++ b/molecule/default/tasks/apply.yml
@@ -761,6 +761,81 @@
         that:
           - deploy_after_serviceaccount_removal is failed
 
+    - name: Add a secret
+      k8s:
+        definition:
+          apiVersion: v1
+          kind: Secret
+          metadata:
+            name: apply-secret
+            namespace: "{{ apply_namespace }}"
+          type: Opaque
+          stringData:
+            foo: bar
+      register: k8s_secret
+
+    - name: Check secret was created
+      assert:
+        that:
+          - k8s_secret is changed
+          - k8s_secret.result.data.foo
+
+    - name: Add same secret
+      k8s:
+        definition:
+          apiVersion: v1
+          kind: Secret
+          metadata:
+            name: apply-secret
+            namespace: "{{ apply_namespace }}"
+          type: Opaque
+          stringData:
+            foo: bar
+      register: k8s_secret
+
+    - name: Check nothing changed
+      assert:
+        that:
+          - k8s_secret is not changed
+
+    - name: Add same secret with check mode on
+      k8s:
+        definition:
+          apiVersion: v1
+          kind: Secret
+          metadata:
+            name: apply-secret
+            namespace: "{{ apply_namespace }}"
+          type: Opaque
+          stringData:
+            foo: bar
+      check_mode: yes
+      register: k8s_secret
+
+    - name: Check nothing changed
+      assert:
+        that:
+          - k8s_secret is not changed
+
+    - name: Add same secret with check mode on using data
+      k8s:
+        definition:
+          apiVersion: v1
+          kind: Secret
+          metadata:
+            name: apply-secret
+            namespace: "{{ apply_namespace }}"
+          type: Opaque
+          data:
+            foo: YmFy
+      check_mode: yes
+      register: k8s_secret
+
+    - name: Check nothing changed
+      assert:
+        that:
+          - k8s_secret is not changed
+
   always:
     - name: Remove namespace
       k8s:
diff --git a/plugins/module_utils/common.py b/plugins/module_utils/common.py
index 788c9df8..2e2bc6ed 100644
--- a/plugins/module_utils/common.py
+++ b/plugins/module_utils/common.py
@@ -18,6 +18,7 @@
 from __future__ import absolute_import, division, print_function
 __metaclass__ = type
 
+import base64
 import time
 import os
 import traceback
@@ -28,7 +29,7 @@ from distutils.version import LooseVersion
 
 from ansible.module_utils.basic import AnsibleModule, missing_required_lib
 from ansible.module_utils.six import iteritems, string_types
-from ansible.module_utils._text import to_native
+from ansible.module_utils._text import to_native, to_bytes, to_text
 from ansible.module_utils.common.dict_transformations import dict_merge
 from ansible.module_utils.parsing.convert_bool import boolean
 
@@ -690,7 +691,7 @@ class K8sAnsibleMixin(object):
         else:
             if self.apply:
                 if self.check_mode:
-                    ignored, patch = apply_object(resource, definition)
+                    ignored, patch = apply_object(resource, _encode_stringdata(definition))
                     if existing:
                         k8s_obj = dict_merge(existing.to_dict(), patch)
                     else:
@@ -721,7 +722,7 @@ class K8sAnsibleMixin(object):
 
             if not existing:
                 if self.check_mode:
-                    k8s_obj = definition
+                    k8s_obj = _encode_stringdata(definition)
                 else:
                     try:
                         k8s_obj = resource.create(definition, namespace=namespace).to_dict()
@@ -757,7 +758,7 @@ class K8sAnsibleMixin(object):
 
             if existing and force:
                 if self.check_mode:
-                    k8s_obj = definition
+                    k8s_obj = _encode_stringdata(definition)
                 else:
                     try:
                         k8s_obj = resource.replace(definition, name=name, namespace=namespace, append_hash=self.append_hash).to_dict()
@@ -781,7 +782,7 @@ class K8sAnsibleMixin(object):
 
             # Differences exist between the existing obj and requested params
             if self.check_mode:
-                k8s_obj = dict_merge(existing.to_dict(), definition)
+                k8s_obj = dict_merge(existing.to_dict(), _encode_stringdata(definition))
             else:
                 if LooseVersion(self.openshift_version) < LooseVersion("0.6.2"):
                     k8s_obj, error = self.patch_resource(resource, definition, existing, name,
@@ -858,3 +859,12 @@ class KubernetesAnsibleModule(AnsibleModule, K8sAnsibleMixin):
 
         self.warn("class KubernetesAnsibleModule is deprecated"
                   " and will be removed in 2.0.0. Please use K8sAnsibleMixin instead.")
+
+
+def _encode_stringdata(definition):
+    if definition['kind'] == 'Secret' and 'stringData' in definition:
+        for k, v in definition['stringData'].items():
+            encoded = base64.b64encode(to_bytes(v))
+            definition.setdefault('data', {})[k] = to_text(encoded)
+        del definition['stringData']
+    return definition
diff --git a/tests/unit/module_utils/test_common.py b/tests/unit/module_utils/test_common.py
new file mode 100644
index 00000000..5eb4621b
--- /dev/null
+++ b/tests/unit/module_utils/test_common.py
@@ -0,0 +1,39 @@
+# -*- coding: utf-8 -*-
+# Copyright: (c) 2021, Ansible Project
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+from __future__ import absolute_import, division, print_function
+
+__metaclass__ = type
+
+
+from ansible_collections.community.kubernetes.plugins.module_utils.common import (
+    _encode_stringdata,
+)
+
+
+def test_encode_stringdata_modifies_definition():
+    definition = {
+        "apiVersion": "v1",
+        "kind": "Secret",
+        "type": "Opaque",
+        "stringData": {
+            "mydata": "ansiβle"
+        }
+    }
+    res = _encode_stringdata(definition)
+    assert "stringData" not in res
+    assert res["data"]["mydata"] == "YW5zac6ybGU="
+
+
+def test_encode_stringdata_does_not_modify_data():
+    definition = {
+        "apiVersion": "v1",
+        "kind": "Secret",
+        "type": "Opaque",
+        "data": {
+            "mydata": "Zm9vYmFy"
+        }
+    }
+    res = _encode_stringdata(definition)
+    assert res["data"]["mydata"] == "Zm9vYmFy"