Objectives: Poly(ADP-ribose) polymerase (PARP) inhibitors are expensive and their use is expanding. We aimed to evaluate cost sharing patterns between patients, payors, and financial assistance programs. Methods: We identified ovarian cancer patients prescribed a PARP inhibitor from 5/2015–9/2019 using our pharmacy database. Cost information was collected for patients who filled their prescription at our specialty pharmacy. We calculated descriptive statistics for monthly PARP inhibitor costs for patients, payors, and financial assistance programs. We used Wilcoxon rank sum tests to evaluate monthly costs based on insurance characteristics. Results: Seventy-six patients filled 94 different PARP inhibitor prescriptions with 42 (45%) prescriptions obtained using any type of financial assistance program. We analyzed 232 prescription months for the 41 prescriptions with available cost data. This included 18 (44%) prescriptions for rucaparib, 18 (44%) for niraparib, and 5 (12%) for olaparib. The total monthly drug cost was average $12,422 and median $13,700. The monthly out-of-pocket (OOP) cost for patients was average $46 and median $0 (IQR $0–4). Payors had the highest monthly costs with average $12,019 and median $13,662 (IQR $9914-14,709). Financial assistance programs contributed average $358 and median $0 per month (IQR $0–150). Patients with public (p<0.01) or Medicare insurance (p<0.01) had higher OOP costs than without. Conclusions: OOP costs were generally low with 75% of patients paying <$5 per month. While limited by small sample size at a single institution, financial assistance programs appear to play a critical role to ensure access to PARP inhibitors as nearly 50% of patients utilized these programs.