Nanoparticles have comprehensively affected various sights of human life. Through the wide range of claims about nanosized particles and their functions, biomedical applications are of much interest among health care researchers due to the nanoparticles' potential for use in the process of disease diagnosis, control and treatment. In this regard, inorganic nanoparticles, which have high potential in diagnostic and therapeutic systems, have recently received much attention in oncology. Although inorganic nanoparticles initially seemed an appropriate tool for cancer imaging and diagnosis, their ability to attack cancerous cells as anticancer drugs or carriers in other drugs has also demonstrated promising results. The present review primarily provides a brief survey of various studies in which metal nanoparticles such as gold, silver, iron oxide, and metalloid nanoparticles viz. tellurium and bismuth were exploited for therapeutic or diagnostic purposes in oncology. Then the application of selenium nanoparticles as a therapeutic agent against cancer in in vitro and in vivo studies is reviewed in detail. Although inorganic nanoparticles seem to be useful tools for cancer imaging and diagnosis, their potential for attacking cancerous cells as anticancer substances or even carriers for anticancer medications should not be underestimated.