In this paper, Bacillus megaterium A9an was selected as an efficient Bacillus-pToducmg polyhydroxyalkanoate (PHA) on the basis of intracellular PHA detection by the nile red staining method and PHA determination by spectrophotometry. A sequencing batch reactor (SBR) cycle of 24 h was fed with a synthetic wastewater and seeded with a pure culture of the selected Bacillus-producing PHA to generate an activated sludge. Two anoxic/aerobic times of 4 W18 h and 2 h/20 h were used to determine the most suitable operational condition for conversion of wastewater to PHA. The results showed that the PHA production, the total Kjeldahl nitrogen (TKN) and orthophosphate removal efficiencies were higher at the longer anoxic time while the COD removal efficiency was higher at the shorter anoxic time. Under anoxic/aerobic times of 4 W18 h, the highest average PHA production and yield of 1.4054 g l ^-1 and 74.0% as dry sludge weight was found. The highest average COD, TKN and orthophosphate removal efficiencies were 87.5%, 80.0% and 57.2%, respectively. Thus, the use of B. megaterium A9an in SBR operating at the anoxic/aerobic times of 4 W18 h could offer a promising approach for PHA production along with a high performance in wastewater treatment. © IDOSI Publications, 2011.