This work investigate the chlorine tolerance and antifouling properties of sulfonated polyaniline (S-PANI) ultrafiltration (UF) membrane. S-PANI was synthesized from aniline monomer through chemical oxidative polymerisation. S-PANI polymer powder was dissolved in N-methyl-pyrrolidone (NMP) up to 20% wt to form casting solution along with anti-gelling agent 4-methylpyridine (4MP). S-PANI membrane chlorine resistance was tested at 250 ppm free chlorine for three consecutive days at different pH values (4.5, 7.4 and 10.5). Membrane chlorine resistance was scrutinised at 100% hypochlorous acid, 100% hypochlorite and 50% of the last two chlorine species. The membrane permeance and rejection were retained before and after chlorination with BSA rejection over 95%. FTIR spectroscopy shows no changes in chemical structure. The permeance, rejection and SEM images demonstrated that the slight change in membrane characteristics was more pH dependent than chlorine exposure. The membrane was doped, rearranged and the shrunk under low pH conditions (4.5) in contrast with higher pH values (10.5). The membrane surface charge was increased as pH rises and decreased beyond exposure to chlorine. Contact angle dropped by 22.0% after soaking S-PANI membrane with chlorine solution at pH 4.5 and 7.4 whilst, no noticeable change was observed at pH 10.5. S-PANI membrane antifouling was compared with commercial polyethersulfone (PES) membrane. The flux recovery ratio was calculated for both membranes and S-PANI proved to retain higher antifouling property than PES with a flux recovery ratio (FRR) of 85.8% compared to 62% solely with DI cleaning.