Breast cancer stands as the leading cause of cancer-related deaths among women worldwide. Endocannabinoids and their exogenous analogs, e.g., tetrahydrocannabinol, exhibit antitumor effects in various animal models of cancer. However, several studies have shown that under certain conditions, treatment with cannabinoids can stimulate the proliferation of cancer cells in vitro and disrupt the immune system’s involvement in suppressing tumors. Additionally, conflicting reports exist regarding the antitumor role of endocannabinoid system in cancer. This review aims to consider the main mechanisms of action of key ligands and receptors of the endocannabinoid system within the context of breast cancer. © Eco-Vector, 2024.