diff --git a/Lib/multiprocessing/dummy/__init__.py b/Lib/multiprocessing/dummy/__init__.py
index 403f5e5198..fc01ecfa32 100644
--- a/Lib/multiprocessing/dummy/__init__.py
+++ b/Lib/multiprocessing/dummy/__init__.py
@@ -21,6 +21,7 @@ import threading
 import sys
 import weakref
 import array
+import warnings
 
 from .connection import Pipe
 from threading import Lock, RLock, Semaphore, BoundedSemaphore
@@ -39,6 +40,7 @@ class DummyProcess(threading.Thread):
         self._children = weakref.WeakKeyDictionary()
         self._start_called = False
         self._parent = current_process()
+        self._joined = False
 
     def start(self):
         if self._parent is not current_process():
@@ -50,6 +52,15 @@ class DummyProcess(threading.Thread):
             self._parent._children[self] = None
         threading.Thread.start(self)
 
+    def join(self):
+        self._joined = True
+        super().join()
+
+    def __del__(self, _warn=warnings.warn):
+        if not self._joined:
+            _warn("thread %r not joined" % self,
+                  ResourceWarning, source=self)
+
     @property
     def exitcode(self):
         if self._start_called and not self.is_alive():
diff --git a/Lib/multiprocessing/popen_fork.py b/Lib/multiprocessing/popen_fork.py
index 685e8daf77..4e0285b9d3 100644
--- a/Lib/multiprocessing/popen_fork.py
+++ b/Lib/multiprocessing/popen_fork.py
@@ -1,5 +1,6 @@
 import os
 import signal
+import time
 
 from . import util
 
diff --git a/Lib/multiprocessing/process.py b/Lib/multiprocessing/process.py
index cd592d0bdf..6cbe80b8f5 100644
--- a/Lib/multiprocessing/process.py
+++ b/Lib/multiprocessing/process.py
@@ -18,6 +18,7 @@ import sys
 import signal
 import itertools
 import threading
+import warnings
 from _weakrefset import WeakSet
 
 #
@@ -160,6 +161,11 @@ class BaseProcess(object):
             _children.discard(self)
             return False
 
+    def __del__(self, _warn=warnings.warn):
+        if self._popen is not None:
+            _warn("process %r is still running" % self,
+                  ResourceWarning, source=self)
+
     def close(self):
         '''
         Close the Process object.