Microbial kinetics of a hybrid upflow anaerobic sludge blanket (UASB) reactor were investigated when treating chemical synthesis–based pharmaceutical wastewater. Monod, Grau first-order, Grau second-order, Stover-Kincannon, Chen & Hashimoto kinetic models were applied to the hybrid reactor. The second-order model was found to be the most appropriate model for the hybrid reactor (R2 = 0.99) and offers the best description of the process. The substrate removal rate constant (k2S) was found to be 4.91 d-1.