In the current study, styrene was removed anaerobically from wastewaters at temperatures of 35 degrees C, 25 degrees C, and 15 degrees C and concentration range of 20-150 ppm in the presence of ethanol as a co-substrate and co-solvent. Maximum styrene removal of 93% was achieved at 35 degrees C. The volatilization of styrene was negligible at about 2% at all experimented temperatures. The average special methane yield (SMY) at 35 degrees C was 4.14- and 225-times higher than that of at T = 25 degrees C and T = 15 degrees C, respectively, but no methane was produced in the absence of ethanol. The proteins content of the soluble microbial product (SMP) and extracellular polymeric substance (EPS) was much higher than the carbohydrate content. At styrene concentration > 80 ppm, SMY, SMP, and EPS dropped sharply. The results confirmed the well performance of anaerobic microorganisms in removing styrene from wastewater and biogas production at mesophilic condition.