diff --git a/changelogs/fragments/remove-warnings-retval.yml b/changelogs/fragments/remove-warnings-retval.yml
new file mode 100644
index 00000000000..aa887c021a7
--- /dev/null
+++ b/changelogs/fragments/remove-warnings-retval.yml
@@ -0,0 +1,2 @@
+minor_changes:
+  - "modules - use ``AnsibleModule.warn`` instead of passing ``warnings`` to ``exit_json`` or ``fail_json`` which is deprecated."
diff --git a/lib/ansible/modules/assemble.py b/lib/ansible/modules/assemble.py
index ff570aee1b9..35d435381e4 100644
--- a/lib/ansible/modules/assemble.py
+++ b/lib/ansible/modules/assemble.py
@@ -181,7 +181,7 @@ def assemble_from_fragments(src_path, delimiter=None, compiled_regexp=None, igno
     return temp_path
 
 
-def cleanup(path, result=None):
+def cleanup(module, path, result=None):
     # cleanup just in case
     if os.path.exists(path):
         try:
@@ -189,7 +189,7 @@ def cleanup(path, result=None):
         except (IOError, OSError) as e:
             # don't error on possible race conditions, but keep warning
             if result is not None:
-                result['warnings'] = ['Unable to remove temp file (%s): %s' % (path, to_native(e))]
+                module.warn('Unable to remove temp file (%s): %s' % (path, to_native(e)))
 
 
 def main():
@@ -261,7 +261,7 @@ def main():
             (rc, out, err) = module.run_command(validate % path)
             result['validation'] = dict(rc=rc, stdout=out, stderr=err)
             if rc != 0:
-                cleanup(path)
+                cleanup(module, path)
                 module.fail_json(msg="failed to validate: rc:%s error:%s" % (rc, err))
         if backup and dest_hash is not None:
             result['backup_file'] = module.backup_local(dest)
@@ -269,7 +269,7 @@ def main():
         module.atomic_move(path, dest, unsafe_writes=module.params['unsafe_writes'])
         changed = True
 
-    cleanup(path, result)
+    cleanup(module, path, result)
 
     # handle file permissions
     file_args = module.load_file_common_arguments(module.params)
diff --git a/lib/ansible/modules/cron.py b/lib/ansible/modules/cron.py
index 8abfca172fa..925004b83f2 100644
--- a/lib/ansible/modules/cron.py
+++ b/lib/ansible/modules/cron.py
@@ -618,7 +618,6 @@ def main():
 
     changed = False
     res_args = dict()
-    warnings = list()
 
     if cron_file:
 
@@ -627,8 +626,8 @@ def main():
 
         cron_file_basename = os.path.basename(cron_file)
         if not re.search(r'^[A-Z0-9_-]+$', cron_file_basename, re.I):
-            warnings.append('Filename portion of cron_file ("%s") should consist' % cron_file_basename +
-                            ' solely of upper- and lower-case letters, digits, underscores, and hyphens')
+            module.warn('Filename portion of cron_file ("%s") should consist' % cron_file_basename +
+                        ' solely of upper- and lower-case letters, digits, underscores, and hyphens')
 
     # Ensure all files generated are only writable by the owning user.  Primarily relevant for the cron_file option.
     os.umask(int('022', 8))
@@ -693,7 +692,7 @@ def main():
         if do_install:
             for char in ['\r', '\n']:
                 if char in job.strip('\r\n'):
-                    warnings.append('Job should not contain line breaks')
+                    module.warn('Job should not contain line breaks')
                     break
 
             job = crontab.get_cron_job(minute, hour, day, month, weekday, job, special_time, disabled)
@@ -734,7 +733,6 @@ def main():
     res_args = dict(
         jobs=crontab.get_jobnames(),
         envs=crontab.get_envnames(),
-        warnings=warnings,
         changed=changed
     )
 
diff --git a/lib/ansible/modules/git.py b/lib/ansible/modules/git.py
index f7b5ae9752f..9c21466e6ab 100644
--- a/lib/ansible/modules/git.py
+++ b/lib/ansible/modules/git.py
@@ -317,11 +317,6 @@ remote_url_changed:
     returned: success
     type: bool
     sample: True
-warnings:
-    description: List of warnings if requested features were not available due to a too old git version.
-    returned: error
-    type: str
-    sample: git version is too old to fully support the depth argument. Falling back to full checkouts.
 git_dir_now:
     description: Contains the new path of .git directory if it is changed.
     returned: success
@@ -1240,7 +1235,7 @@ def main():
     archive_prefix = module.params['archive_prefix']
     separate_git_dir = module.params['separate_git_dir']
 
-    result = dict(changed=False, warnings=list())
+    result = dict(changed=False)
 
     if module.params['accept_hostkey']:
         if ssh_opts is not None:
diff --git a/lib/ansible/modules/pip.py b/lib/ansible/modules/pip.py
index 2d520618f12..39e3457696a 100644
--- a/lib/ansible/modules/pip.py
+++ b/lib/ansible/modules/pip.py
@@ -814,10 +814,8 @@ def main():
         elif requirements:
             cmd.extend(['-r', requirements])
         else:
-            module.exit_json(
-                changed=False,
-                warnings=["No valid name or requirements file found."],
-            )
+            module.warn("No valid name or requirements file found.")
+            module.exit_json(changed=False)
 
         if module.check_mode:
             if extra_args or requirements or state == 'latest' or not name: