BRCA (BReast CAncer gene) mutations are considered strong risk factors in females and males cancers, these include breast, male breast (although rare), ovarian, prostate, pancreatic, and melanoma skin cancers. This paper reviews the literature concerning the association between BRCA and the response rate to poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPi) in breast and ovarian cancer patients. Recent evidence shows that PARPi can be utilized as a base for monotherapy strategies and a broad spectrum of molecular cancers. BRCA1/BRCA2 mutations enhance the risk for developing ovarian and breast cancer, amongst others that are caused either by somatic or germline mutations. PARPi begins the repair pathway of the single-stranded DNA breakage, which is considered the most common form of damage, with the help of certain key PARP enzymes. Olaparib was the first approved PARPi drug by the European Medicine Agency (EMA) and the American Food and Drug Administration (FDA) to treat patients with recurrent BRCA-mutated epithelial ovarian cancer after receiving three or more previous chemotherapies. Furthermore, the FDA approved olaparib to manage patients with HER2-negative, BRCA-mutated, and metastatic breast cancers managed previously through chemotherapy. The studies show that using olaparib for maintenance treatment results in a significantly longer progression-free survival and a slightly better overall survival rate among breast and ovarian cancer patients. Certain studies have shown that olaparib maintenance treatment was mostly prosperous and well-endured among advanced BRCA-mutated ovarian cancers.