diff --git a/Doc/library/subprocess.rst b/Doc/library/subprocess.rst
--- a/Doc/library/subprocess.rst
+++ b/Doc/library/subprocess.rst
@@ -705,22 +705,30 @@
 
 .. attribute:: Popen.stdin
 
-   If the *stdin* argument was :data:`PIPE`, this attribute is a :term:`file
-   object` that provides input to the child process.  Otherwise, it is ``None``.
-
+   If the *stdin* argument was :data:`PIPE`, this attribute is a
+   writeable stream object as returned by :meth:`io.open`. If the
+   *universal_newlines* argument was True, the stream is a character
+   stream, otherwise it is a byte stream. If the *stdin* argument was
+   not :data:`PIPE`, this attribute is ``None``.
 
 .. attribute:: Popen.stdout
 
-   If the *stdout* argument was :data:`PIPE`, this attribute is a :term:`file
-   object` that provides output from the child process.  Otherwise, it is ``None``.
-
+   If the *stdout* argument was :data:`PIPE`, this attribute is a
+   readable stream object as returned by :meth:`io.open`. Reading from
+   the stream provides output from the child process. If the
+   *universal_newlines* argument was True, the stream is a character
+   stream, otherwise it is a byte stream. If the *stdout* argument was
+   not :data:`PIPE`, this attribute is ``None``.
+               
 
 .. attribute:: Popen.stderr
 
-   If the *stderr* argument was :data:`PIPE`, this attribute is a :term:`file
-   object` that provides error output from the child process.  Otherwise, it is
-   ``None``.
-
+   If the *stderr* argument was :data:`PIPE`, this attribute is a
+   readable stream object as returned by :meth:`io.open`. Reading from
+   the stream provides output from the child process. If the
+   *universal_newlines* argument was True, the stream is a character
+   stream, otherwise it is a byte stream. If the *stderr* argument was
+   not :data:`PIPE`, this attribute is ``None``.
 
 .. attribute:: Popen.pid
 
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -220,6 +220,9 @@
 - Issue #19286: Directories in ``package_data`` are no longer added to
   the filelist, preventing failure outlined in the ticket.
 
+- Issue #17814: Improve documentation of stream objects that are
+  created by subprocess.Popen. Patch by Nikolaus Rath.
+
 IDLE
 ----