In recent years, awareness regarding micro-nanoplastics' (MNPs) potential effects on human health has progressively increased. Despite a large body of evidence regarding the origin and distribution of MNPs in the environment, their impact on human health remains to be determined. In this context, there is a major need to address their potential carcinogenic risks, since MNPs could hypothetically mediate direct and indirect carcinogenic effects, the latter mediated by particle-linked chemical carcinogens. Currently, evidence in this field is scarce and heterogeneous, but the reported increased incidence of malignant tumors among younger populations, together with the ubiquitous environmental abundance of MNPs, are rising a global concern regarding the possible role of MNPs in the development and progression of cancer. In this review, we provide an overview of the currently available evidence in eco-toxicology, as well as methods for the identification and characterization of environmental MNP particulates and their health-associated risks, with a focus on cancer. In addition, we suggest possible routes for future research in order to unravel the carcinogenetic potential of MNP exposure and to understand prognostic and preventive implications of intratumoral MNPs.