Objective: To assess patient-reported health-related quality of life (HRQoL) in patients with ovarian cancer (OC) who received niraparib as first-line maintenance therapy. Methods: PRIMA/ENGOT-OV26/GOG-3012 (NCT02655016) enrolled patients with newly diagnosed advanced OC who responded to first-line platinum-based chemotherapy. Patients were randomized (2:1) to niraparib or placebo once daily in 28-day cycles until disease progression, intolerable toxicity, or death. HRQoL was assessed as a prespecified secondary end point using patient-reported responses to the European Organisation for Research and Treatment of Cancer QOL Questionnaire (EORTC QLQ-C30), the EORTC QLQ Ovarian Cancer Module (EORTC QLQ-OV28), the Functional Assessment of Cancer Therapy–Ovarian Symptom Index (FOSI), and EQ-5D-5L questionnaires. Assessments were collected at baseline and every 8 weeks (±7 days) for 56 weeks, beginning on cycle 1/day 1, then every 12 weeks (±7 days) thereafter while the patient received study treatment. Results: Among trial participants (niraparib, n = 487; placebo, n = 246), PRO adherence exceeded 80% for all instruments across all cycles. Patients reported no decline over time in HRQoL measured via EORTC QLQ-C30 Global Health Status/QoL and FOSI overall scores. Scores for abdominal/gastrointestinal symptoms (EORTC QLQ-OV28) and nausea and vomiting, appetite loss, and constipation (EORTC QLQ-C30) were higher (worse symptoms) in niraparib-treated patients than placebo-treated patients; except for constipation, these differences resolved over time. Patients did not self-report any worsening from baseline of fatigue, headache, insomnia, or abdominal pain on questionnaires. Conclusions: Despite some early, largely transient increases in gastrointestinal symptoms, patients with OC treated with niraparib first-line maintenance therapy reported no worsening in overall HRQoL.