As the typical organic matter, humic acids (HAs) were studied to explore its effect on the degradation of tetrabromobisphenol A (TBBPA) in anaerobic co-metabolic biodegradation systems. The highest degradation rate (86.9%) and lowest half-life (19.66 h) for TBBPA were obtained in the C-HA-T system (anaerobic co-metabolic reactor with glucose-HA/TBBPA as substrate), which illustrated that the efficiency of the biodegradation of TBBPA was improved due to the addition of HA. The 1,3-dibromo-2-methoxy-5-(2-(p-tolyloxy)propan-2-yl) benzene and 2,6-dibromo-4-(prop-1-en-2-yl)phenyl acetate were detected as the intermediate metabolites of TBBPA, which can conclude that HA has changed the biodegradation pathway of TBBPA. Further, the analysis of microbial diversity showed that Azoarcus was most likely responsible for the biodegradation of TBBPA in C-HA-T.