Aim of this study was to evaluate the anaerobic co-digestion of diluted poultry manure (DPM) and used cooking oil (UCO). Mixtures of DPM with different UCO dosages (1 to 6% v/v) were prepared using a high-shear emulsifier and digested in batch anaerobic reactors. Increasing the UCO dosage resulted in a respective increase of the emulsion COD (from initially 64 to 182 g/L) however the stability of the emulsion was adversely affected. The optimum UCO dosage (1.5-2.0% v/v) was further digested in a semi-continuous mesophilic anaerobic reactor, to assess the feasibility of the process at OLR up to 8 g/Ld. The anaerobic reactor was stable, giving a biogas yield of 0.45 L/gCOD, with low supernatant COD (6 g/L), negligible VFA accumulation and without foaming.