H 2 S and NH 3 are toxic, corrosive and odorous gases that often co-exist in gas streams emitted from industrial processes, including biogas produced in anaerobic digestion plants. A hollow fibre membrane bioreactor (HFMB) was tested for simultaneous biological removal of H 2 S and NH 3 from raw biogas. The HFMB achieved a removal efficiency (RE) > 99% for treating up to 1850, 915 and 1200 ppm v of H 2 S at an empty bed residence time (EBRT) of 187, 92 and 46 s, respectively. The RE of NH 3 was > 99% when the inlet NH 3 concentrations were up to 460, 355 and 750 ppm v at an EBRT of 187, 92 and 46 s, respectively. At an EBRT of 46 s, the RE of H 2 S and NH 3 was in the range of 85–97 and 73–95%, respectively, for inlet biogas laden with 1200–1700 ppm v of H 2 S and 750–1050 ppm v of NH 3 . The critical loading rates of H 2 S and NH 3 were about 150 and 40 g m −3 h −1 , respectively. S 0 (52%), SO 4 2 − (48%) and N 2 (92%) were the end products of the H 2 S and NH 3 bioconversion. Different sulfide oxidizers including aerobic (e.g. Smithella sp., Sulfuricurvum sp. and Thiomonas sp.) and anoxic (e.g. Rhodanobacter sp., Sulfuritalea sp. and Thiobacillus sp.) chemolithotrophs contributed to the H 2 S bioconversion. Aerobic (e.g. Pseudomonas sp., Stenotrophomonas sp. and Nitrosospira sp.) and Fe(III) dependent anaerobic (e.g. Clostridium_sensu_stricto_12 sp., Rhodoferax sp. and Dechloromonas sp.) ammonium oxidizers contributed to the NH 3 bioconversion. Denitrifiers including denitrifying phosphorus accumulating organisms (e.g Candidatus_Contendobacter sp.) contributed to the denitrification process. • Hydrophilic polyethersulfone HFMB simultaneously treated H 2 S and NH 3 from raw biogas. • Maximum H 2 S and NH 3 flux through membrane module was 1.94 and 0.55 g m -2 day -1 , respectively. • The critical loading rate of H 2 S and NH 3 was close to 150 and 40 g m -3 h -1 , respectively, at an EBRT of 46 s. • Outlet/inlet CH 4 ratio ( ∼ 0.99) confirmed low ( < 1%) biogas dilution in the HFMB. • Both aerobic and anoxic processes contributed to H 2 S and NH 3 bioconversion in the HFMB.