Recently, microbial fuel cells (MFCs) considered as a promising technology for direct conversion of biochemical energy into electrical energy. The new technology is environment friendly and efficient for recovering bio-electricity and removing organic wastes. That's why, it is attracting the great attention to the scientific community. Different substrates had been used in MFCs as food for bacteria. Landfill leachate showed a promising feedstock for MFCs system. In this study, two identical single chamber air-cathode MFCs (Volume, 1250 ml) with carbon brushes as anode electrode and Platinum (Pt) coated carbon cloth as cathode electrode was used to investigate the bio-electrical performance for two different concentrations of diluted landfill leachate. The system operated with 8 hours hydraulic retention time (HRT). The MFCs were operated in continuous mode after inoculation of microbial community using raw domestic wastewater for 30 days. The COD content of the raw wastewater used for inoculation was 376-593 mg/L. The MFC produced 161.9 mW/m2 of power density with an internal resistance of Rint = 36 12 during inoculation period, when domestic wastewater was the sole substrate for bacteria. Then the systems were operated with two mixtures of leachate and wastewater as 1:10 (leachate: wastewater) and 1:5 (leachate: wastewater). The mixtures, 1:10 and 1:5 (leachate: wastewater) contained COD as 2,588-4,008 mg/L and 4,286- 6,068 mg/L, respectively. Each mixtures were used as substrates for 5 days during power optimization period. With the ratio of 1:5 mixture, the maximum power density and columbic efficiency (CE) of the MFCs were observed as 1,031 mW/m2 and 11.1%, respectively, for an observed Rint = 6 12. For the ratio of mixture 1:10 (leachate/wastewater), the power density and Ce reached to 775 mW/m2 (Rint = 62) and 11.7% respectively. Increasing the fraction of leachate into the influent substrates of the MFCs showed remarkable improvement of recovering power and coulombic efficiency. The performances of COD and ammonium removal by the MFC systems were observed as 28.2% and 8.2% (for 1:10 mixture) and 23.2% and 4.7% (for 1:5 mixture), respectively. The higher removal of COD and ammonia were observed in case of low concentration of leachate in wastewater, whereas, the higher production of power and columbic efficiency were observed in case of high concentration of leachate in wastewater. The bio electrochemical performances of the MFCs revealed that the system had a great potential for recovering electrical power and removing contaminants from wastewater and leachate. As a new promising technology, the MFC system needs lot of improvement in terms of reactor design, electrode materials, and operating parameters as pH, temperature, electrolytic conductivity and substrate loading.