The effect of addition of kitchen wastewater (KWW) on H2 fermentation of municipal food waste (MFW) was investigated in a mesophillic anaerobic baffled reactor (ABR). A better H2 production of 5.54 ± 0.9 lH2d−1., and H2 yield of 164 ± 22 mlH2gCOD removed−1d−1., was achieved for co-digestion of MFW+KWW as compared to MFW diluted with raw water at a mixing ratio of 1:2, respectively. However, co-digestion process was strongly dependent on the applied pH, COD/TKj-N ratio, and hydraulic retention time (HRT). At pH value of 5, H2 potential (P) and maximum H2 production rate (Rm) were 6912 ml and 141 mlh−1., which were dropped with increasing pH values between 6.2 and 9.0. H2 yield increased from 93.2 ± 12 to 150.9 ± 7 mlH2gVS removed−1d−1., when the COD/TKj-N ratio was increased from 12 to 24.1. Nevertheless, a further increase in COD/TKj-N ratio to greater than 24.1 resulted in a significant drop in H2 yield. Increasing the HRT from 1.82 to 4.6 d., significantly (p < 0.01) increased the H2 yield from 156 ± 73...