In this study, the biological and physical impacts of leachate recycling at Odayeri sanitary landfill are investigated, where municipal solid wastes (MSW) are dumped on the European side of Istanbul. The quantity of landfill gas (LFG), its methane content, and also topographic changes are observed during the 14 months of the test period in and out of the test area. The results indicated that leachate recirculation enhances gas production rate and CH4 fraction of LFG, but reduces waste stabilization time. LFG quantity is increased by about 10% in the test area outside and CH4 fraction of LFG from 48% to 57%. Settling of the test area is observed to be 5% higher than the in non-recirculation area.