The purpose of this investigation is to study the effect of biogas mixing on the combustion and emission characteristics of DME fueled diesel engine. Combustion performance was assessed in terms of combustion pressure, rate of heat release (ROHR), ignition delay, and an indicated mean effective pressure (IMEP). NO, soot, HC and CO emissions were also analyzed using an emission analyzer. Increase in biogas mixing ratio caused a decrease in peak combustion pressure, ignition retardation and reduction in rate of combustion pressure increase. Increase in biogas also induced a decrease in the peak value and gradient of ROHR. Injection and ignition timings showed a linear correlation regardless of biogas mixing ratio when DME was injected toward the piston bowl. At the same injection timing, the increase of biogas caused a decrease in IMEP when DME was injected into the piston bowl. When DME was injected toward the crevice and squish region, IMEP increased as the biogas mixing ratio increased, and IMEP showed a linear correlation with SOL ISNOx emissions decreased with the increase in biogas. The soot emissions level was close to zero in all test conditions. However, ISHC and ISCO emissions showed an increasing trend with increasing biogas mixing ratio. (C) 2014 Elsevier Ltd. All rights reserved.