Various antibiotics have been used in the treatment of cancers, via their anti-proliferative, pro-apoptotic and anti-epithelial-mesenchymal-transition (EMT) capabilities. However, increasingly studies have indicated that antibiotics may also induce cancer generation by disrupting intestinal microbiota, which further promotes chronic inflammation, alters normal tissue metabolism, leads to genotoxicity and weakens the immune response to bacterial malnutrition, thereby adversely impacting cancer treatment. Despite the advent of high-throughput sequencing technology in recent years, the potential adverse effects of antibiotics on cancer treatments via causing microbial imbalance has been largely ignored. In this review, we discuss the double-edged sword of antibiotics in the field of cancer treatments, explore their potential mechanisms and provide solutions to reduce the potential negative effects of antibiotics.