ABSTRACT Introduction and objective: In recent years, microalgae of the Chlorella genus have been gaining popularity due to their rapid biomass growth, ability to grow in extreme conditions, and diverse range of bioactive substances. They constitute a valuable source of nutrients with high bioavailability and a diverse biochemical profile, which makes them widely used in the food industry. Furthermore, the variety of bioactive compounds contained within them, with proven antioxidant, immunomodulatory, antibacterial, antiviral, anticancer and regenerative properties, is attracting attention of the pharmaceutical and cosmetics industries. Review methods: This article presents the current state of knowledge on the chemopreventive properties of preparations based on microalgae of the Chlorella genus. The review includes original papers available in the PubMed and Google Scholar databases. Brief description of the state of knowledge: The possibility of using preparations based on Chlorella spp. in cancer chemoprevention has been analysed primarily in cell cultures and animal studies. Most of the presented studies focus on the direct impact of these preparations on cancer cell viability and proliferation, as well as the potential for modulating biological processes crucial to carcinogenesis, such as the cell cycle, apoptosis, oxidative stress, and signaling in pathways associated with cancer. The role of Chlorella spp. as a potential adjuvant in oncology therapy and as a cytoprotectant mitigating the adverse effects of chemotherapy is also discussed. Summary: The presented review of the most important in vitro and in vivo research findings indicates the significant chemopreventive potential of preparations based on Chlorella spp.