The source mechanism of the January 25, 2005 Hakkari earthquake is obtained from both P wave first motion polarities and waveform modeling. The source mechanism derived from the P wave motion polarities has indicated a dextral faulting along a NW-SE trending rupture plane while sinistral faulting along a NE_SW trending rupture plane. A point-source waveform inversion technique is applied to the teleseismically recorded P and SH waveforms of the earthquake to derive the source process. The data has been satisfactorily matched using two-subevent source process indicating a complex source process with a relatively large strike-slip faulting subevent that followed by a smaller oblique normal faulting subevent. The fact that the active fault map indicate a NW-SE trending thrust fault and NE-SW trending sinistral Akçalı fault in the near source region has prompted us to select the NE-SW trending nodal planes from both solutions as the fault plane. It is suggested that the earthquake was produced by the Akçalı fault and the faulting is left-lateral. The overall source process implies a predominantly left-lateral faulting (strike=201o, dip=69o, rake=-24o) with a seismic moment of 3.5x1017 Nm (MW≈5.7). A stress changes due to rupture along the Akçalı fault well explained the M ≥4 seismicity after the earthquake, thus supporting a NE-SW striking fault. The Yüksekova-Şemdinli Fault Zone, which produced most of the following seismicity, was considerably stressed. The results further suggest active strike-slip faulting within or in the very neighborhood of the Bitlis Thrust Zone.