To examine the safety and efficacy of niraparib+bevacizumab as first-line maintenance therapy for patients with newly diagnosed advanced ovarian cancer. This multicenter, phase II, single-arm, open-label research enrolled adult patients with stage IIIB to IV ovarian, fallopian tube, or primary peritoneal cancer (NCT03326193). Patients were required to attempt debulking surgery and have a complete response, partial response, or no indication of illness following first-line, platinum-based chemotherapy with more than or equal to 3 cycles of bevacizumab. The primary endpoint was the progression-free survival (PFS) rate at 18 months. Secondary outcomes included PFS, overall survival, and safety. Among the 105 evaluable patients, the PFS rate at 18 months was 62% (95% CI 52–71%) in the overall population and 76% (95% CI 61–87) in the homologous recombination deficient (HRd), 47% (95% CI 31–64%) in the HR proficient (HRp), and 56% (95% CI 31–79%) in the HR not determined (HRnd) subgroups (December 24, 2020, cutoff) (December 24, 2020, cutoff). After a median follow-up time of 28.7 months (IQR, 23.9–32.5 months), the median PFS was 19.6 months (95% CI 16.5–25.1) in the overall population (n=105) and 28.3 months (95% CI 19.9–NE), 14.2 months (95% CI 8.6–16.8), and 12.1 months (95% CI 8.0–NE) in the HRd, HRp, and HRnd subgroups, respectively (June 16, 2021, cutoff) (June 16, 2021, cutoff). The most common any-grade treatment-related side effects (associated with niraparib and/or bevacizumab) were thrombocytopenia (74/105), fatigue (60/105), and anemia (55/105; December 24, 2020, cutoff). Niraparib + bevacizumab first-line maintenance therapy exhibited promising PFS results. Safety was consistent with the established safety profiles of niraparib and bevacizumab as monotherapy.