Microplastics, as an emerging environmental pollutant, have received widespread attention for their potential impact on ecosystems and human health. Microplastics are defined as plastic particles less than 5 millimeters in diameter and can be categorized as primary and secondary microplastics. Primary microplastics usually originate directly from industrial production, while secondary microplastics are formed by the degradation of larger plastic items. Microplastics are capable of triggering cytotoxicity and chronic inflammation, and may promote cancer through mechanisms such as pro-inflammatory responses, oxidative stress and endocrine disruption. In addition, improved microplastics bring new perspectives to cancer therapy, and studies of microplastics as drug carriers are underway, showing potential for high targeting and bioavailability. Although current studies suggest an association between microplastics and certain cancers (e.g., lung, liver, and breast cancers), the long-term effects and specific mechanisms still need to be studied. This review aimed at exploring the carcinogenicity of microplastics and their promising applications in cancer therapy provides important directions for future research and emphasizes the need for multidisciplinary collaboration to address this global health challenge.