Porous, antibacterial and antibiofouling membranes were obtained from immiscible polymer blends using non-solvent induced phase separation. Both antibacterial and antibiofouling was mediated by immobilizing quaternized pyridine derivative on the porous membranes. This was manifested by assessing the metabolic content leakage (K+ ions and nucleic acid) monitored at different time intervals when the membranes were in contact with E.coli (gram negative) and S.aureus (gram positive). Further, the hydrophilic nature of the pyridine derivative led to antibiofouling nature. The hierarchical porous ‘finger-like’ morphology was confirmed by Scanning electron Microscopy. The trans-membrane flux was measured using a cross-flow flux setup. A quantitative study of the antibacterial activity was carried out using a standard plate count method. The modified membranes showed 3-log and 2-log reduction in E. coli and S. aureus respectively in 2 h and 7-log fold reduction in both bacterial strains in 24 h. The oxidative stress generated by the pyridine derivative on both the bacterial strains was assessed by measuring the Reactive Oxygen Species (ROS). The ROS was significantly higher in case of modified membranes which supported the biocidal nature of the pyridine derivative. The antifouling study was carried out by using BSA (Bovine serum albumin) as a model biofoulant. The flux recovery ratio was significantly higher in case of modified membranes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim