Monoethanolamine (MEA) is widely used in many industries and its proper treatment is important for protecting the water environment. As MEA contains an amine group, nitrogen removal by nitrification/denitrification as well as biodegradation of MEA is necessary for wastewater treatment. In this study the effects of adaptation and inhibition of MEA on biological degradation, and the removal of amine were investigated in a laboratory scale sequencing batch reactor (SBR). In addition, the denitrification characteristics of nitrate, and nitrite with MEA as the electron donor, were compared to the other electron donor (acetate). In the aerobic SBR, the removal efficiency of 9,000 mg/L MEA reached 92% at the hydraulic retention time (HRT) of 10.5 days. Ammonium hydrolyzed from the MEA was nitrified after 8 weeks from the start-up showing that adaptation time is needed for nitrification. Non-linear curve fitting of the specific MEA biodegradation gave the maximum specific activity (Vmax), the half saturation constant (Ks), and the inhibition constant (Ki) of 2.81 g/(g VSS·d), 102.1 mg/L, and 1149.6 mg/L, respectively. Batch denitrification showed that MEA is a competitive electron donor to acetate.