Bacterial β-glucuronidases (BGUSs) are an important type of hydrolase produced by gut microbiota and play an important role in tumor development and chemotherapy by deconjugating a large number of endogenous and exogenous glucuronides. In recent years, BGUSs inhibition has emerged as a promising approach to reduce cancer risk and alleviate gastrointestinal toxicity of chemotherapy drugs. However, a growing body of evidence underlines great genetic and structural diversity, functional promiscuity, and varied inhibition propensity of BGUSs, which have posed enormous challenges to identifying BGUSs involved in a specific pathophysiological or pharmacological process and developing effective inhibitors. In this review, we summarize the latest advances in structure and function of BGUSs and review the findings of BGUS-mediated carcinogen reactivation and deconjugation of chemotherapy drugs in recent years, as well as the discovery of BGUSs inhibitors and preclinical investigation of their applications in cancer prevention and drug therapy. Finally, we discuss the prospects of BGUSs inhibition as a new strategy for tumor prevention and drug therapy.