The widespread consumption of antibiotics has raised public concerns due to the potential hazards of antibiotic residues to the environment. Compared to conventional activated sludge processes, biofilm-based wastewater treatment processes show great potential for antibiotic biodegradation due to the abundant microbial communities in biofilms. However, limted review work is available on the underlying antibiotic biodegradation mechanisms and microbial communities to date. This review indicated that metabolism and cometabolism induced by the functional microorganisms were the major biodegradation mechanisms in the biofilm, despite variations among different biofilm-based reactors. The cometabolism induced by autotrophic ammonia oxidizing microorganisms, heterotrophic bacteria or fungi had a significant contribution. Core microbial communities were identified with antibiotic degrading abilities (e.g., Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria), although more efforts are needed to confirm the relationship between microorganisms and antibiotic biodegradation under different operating conditions. The impact of antibiotic exposure was explored to identify its stimulating or inhibiting effects on microbial communities. Generally, biodegradation products of antibiotics in biofilm-based processes had simpler structures and lower molecular weights than those in the activated sludge system. The results indicated the potential of the biofilm-based treatment processes towards efficient removal of antibiotics and conventional pollutants simultaneously, as well as eliminating antimicrobial activities, via feasible regulatory strategies.