diff --git a/docs/Code_Overview.md b/docs/Code_Overview.md
index 1522c60b..207b37f4 100644
--- a/docs/Code_Overview.md
+++ b/docs/Code_Overview.md
@@ -98,9 +98,11 @@ printer object calls, which frequently translate the actions to
 commands to be executed on the micro-controller (as declared via the
 DECL_COMMAND macro in the micro-controller code).
 
-There are three threads in the Klippy host code. The main thread
+There are four threads in the Klippy host code. The main thread
 handles incoming gcode commands. A second thread (which resides
 entirely in the **klippy/serialqueue.c** C code) handles low-level IO
 with the serial port. The third thread is used to process response
 messages from the micro-controller in the Python code (see
-**klippy/serialhdl.py**).
+**klippy/serialhdl.py**). The fourth thread writes debug messages to
+the log (see **klippy/queuelogger.py**) so that the other threads
+never block on log writes.
diff --git a/klippy/klippy.py b/klippy/klippy.py
index cb81364e..6668ef4c 100644
--- a/klippy/klippy.py
+++ b/klippy/klippy.py
@@ -5,7 +5,7 @@
 #
 # This file may be distributed under the terms of the GNU GPLv3 license.
 import sys, optparse, ConfigParser, logging, time, threading
-import gcode, toolhead, util, mcu, fan, heater, extruder, reactor
+import gcode, toolhead, util, mcu, fan, heater, extruder, reactor, queuelogger
 
 class ConfigWrapper:
     def __init__(self, printer, section):
@@ -132,7 +132,7 @@ def main():
         opts.error("Incorrect number of arguments")
     conffile = args[0]
 
-    debuginput = debugoutput = None
+    debuginput = debugoutput = bglogger = None
 
     debuglevel = logging.INFO
     if options.verbose:
@@ -142,8 +142,7 @@ def main():
     if options.outputfile:
         debugoutput = open(options.outputfile, 'wb')
     if options.logfile:
-        logoutput = open(options.logfile, 'wb')
-        logging.basicConfig(stream=logoutput, level=debuglevel)
+        bglogger = queuelogger.setup_bg_logging(options.logfile, debuglevel)
     else:
         logging.basicConfig(level=debuglevel)
     logging.info("Starting Klippy...")
@@ -159,5 +158,8 @@ def main():
         store_dictionary(options.write_dictionary, printer)
     printer.run()
 
+    if bglogger is not None:
+        bglogger.stop()
+
 if __name__ == '__main__':
     main()
diff --git a/klippy/queuelogger.py b/klippy/queuelogger.py
new file mode 100644
index 00000000..8494c6a8
--- /dev/null
+++ b/klippy/queuelogger.py
@@ -0,0 +1,48 @@
+# Code to implement asynchronous logging from a background thread
+#
+# Copyright (C) 2016  Kevin O'Connor <kevin@koconnor.net>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+import logging, threading, Queue
+
+# Class to forward all messages through a queue to a background thread
+class QueueHandler(logging.Handler):
+    def __init__(self, queue):
+        logging.Handler.__init__(self)
+        self.queue = queue
+    def emit(self, record):
+        try:
+            self.format(record)
+            record.msg = record.message
+            record.args = None
+            record.exc_info = None
+            self.queue.put_nowait(record)
+        except Exception:
+            self.handleError(record)
+
+# Class to poll a queue in a background thread and log each message
+class QueueListener(object):
+    def __init__(self, handler):
+        self.handler = handler
+        self.queue = Queue.Queue()
+        self.thread = threading.Thread(target=self._bg_thread)
+        self.thread.start()
+    def _bg_thread(self):
+        while 1:
+            record = self.queue.get(True)
+            if record is None:
+                break
+            self.handler.handle(record)
+    def stop(self):
+        self.queue.put_nowait(None)
+        self.thread.join()
+
+def setup_bg_logging(filename, debuglevel):
+    logoutput = open(filename, 'wb')
+    handler = logging.StreamHandler(logoutput)
+    ql = QueueListener(handler)
+    qh = QueueHandler(ql.queue)
+    root = logging.getLogger()
+    root.addHandler(qh)
+    root.setLevel(debuglevel)
+    return ql