The removal of a synthetic estrogen 17α-ethinylestradiol (EE2) was investigated in submerged membrane bioreactors (MBRs) with simultaneous nitrification–denitrification (SND) and conventional nitrification. The influent EE2 concentration was 500 ng/L as EE2. Using a yeast estrogen screen test, the conventional-MBR (C-MBR) and SND MBR (SND-MBR) removed 57 and 58% of the estrogenic activity (EA) respectively; there was no significant difference in their removal efficiencies. Biodegradation was the dominant removal mechanism for both reactors with KBIO coefficients of 1.5 ± 0.6 and 1.6 ± 0.4 day−1 for the C-MBR and the SND-MBR respectively. Sorption to solid particles removed approximately 1% of influent EA in each reactor; the particle partitioning coefficient, KD, was calculated to be 0.21 ± 0.07 L/(g MLSS) for the C-MBR and 0.27 ± 0.1 L/(g MLSS) for the SND-MBR. These findings suggest that conditions favoring SND in MBRs have no significant impact on EA reduction.