Alternatively, to traditional landfilling, using bioreactor landfilling and anaerobic treatment technology has been increasing recently, which facilitates more controlled conditions for the degradation of wastes. The aim of this study is to investigate the effects of different seed sludges inoculation on the anaerobic degradation performance of the organic fraction of municipal solid wastes (OFMSWs) in the simulated bioreactors. In this respect, Bio-One (TM), Anaerobic, and Karahayit sludge as seed materials were tested for the performance on the degradation of OFMSW. Besides methane quantity and percentage, the leachate characteristics and methanogenic microflora were also determined. At the end of the 90 days, the cumulative methane quantity and percentage of inoculated reactors were higher than the control. The highest methanogen diversity was found at Anaerobic and Karahayit seed sludge inoculated bioreactors. The methanogen species belonging to the Methanobacteriales, Methanomicrobiales, and Methanosarcinales were detected except Methanococcales and Methanopyrales orders in bioreactor systems.