It's not possible to modify a dict inside a dict using a manager from multiprocessing. Ex: from multiprocessing import Process,Manager def f(d): d['1'] = '1' d['2']['1'] = 'Try To Write' if __name__ == '__main__': manager = Manager() d = manager.dict() d['2'] = manager.dict() print d p = Process(target=f, args=(d,)) p.start() p.join() print d d['2'] = 5 print d The output Under Windows 7 (32 Bits) / Python 2.6.2 (32 Bits) is: {'2': {}} {'1': '1', '2': {}} {'1': '1', '2': 5} The output is the same if you change "d['2'] = manager.dict()" to "d['2'] = dict()"