Upflow anaerobic sludge blanket reactor (UASB) has been widely applied in the industries for the treatment of wastewater for better effluent quality and energy recovery in the form of biogas production to reduce the release of greenhouse gases to the environment. Among the microorganisms involved in digestion of organic matter, methanogens are the major microbiological group responsible for methane production; therefore it is necessary to maintain the balance among different microbial populations in anaerobic reactors in order to improve methane production, treatment efficiency as well as the stability of the process. To study the methanogenic diversity present in the anaerobic reactor treating brewery wastewater, real-time quantitative PCR (QPCR) was used. Quantification of the methanogens that is responsible for the production of methane production was carried out. The QPCR results showed high amounts of methane-producing Archaea present in the UASB reactor— thus, extend our understanding on the ability of methanogens to transform organic substrate present in the wastewater into biogas at the optimum reactor performance.