Background: Study 10, a four-part Phase 1/2 study, evaluated oral rucaparib monotherapy in patients with advanced solid tumours. Here we report the final efficacy and safety results in heavily pretreated patients with ovarian cancer who received rucaparib in Study 10 Parts 2A and 2B. Methods: Parts 2A and 2B (Phase 2 portions) enrolled patients with relapsed, high-grade, platinum-sensitive or platinum-resistant, BRCA-mutated ovarian cancer who had received 2–4 (Part 2A) or 3–4 (Part 2B) prior chemotherapies. Patients received oral rucaparib 600 mg twice daily (starting dose). The primary endpoint was the investigator-assessed objective response rate (ORR) by RECIST v1.1. Results: Fifty-four patients were enrolled: 42 in Part 2A (all had platinum-sensitive disease) and 12 in Part 2B (4 with platinum-sensitive disease; 8 with platinum-resistant disease). ORR was 59.3% (95% CI 45.0–72.4%). The median time to onset of the most common nonhaematological treatment-emergent adverse events (TEAEs) was typically early (<56 days) and was later for haematological TEAEs (53–84 days). The median duration of grade ≥3 TEAEs was ≤13 days. Conclusions: In patients with relapsed, platinum-sensitive or platinum-resistant germline BRCA-mutant high-grade ovarian cancer who had received ≥2 prior chemotherapies, rucaparib had robust antitumour activity with a safety profile consistent with prior reports. Clinical trial registration: NCT01482715.