Preclinical studies suggest that β-blockers could exhibit anticancer properties in ovarian cancer. Similar effects have also been reported in observational studies, but their results remain inconsistent and could be impaired by methodological limitations. This study aimed to investigate whether β-blocker use is associated with improved survival in ovarian cancer patients at the Belgian population level.We conducted a population-based study by linking data of the Belgian Cancer Registry with medical claims data of the health insurance companies for patients diagnosed with ovarian cancer between 2004 and 2014. Information on ovarian-cancer-specific deaths was retrieved from mortality records collected by regional governments. Use of β-blockers was modelled as a time-varying covariate in Cox regression models to calculate adjusted hazards ratios (HRs) and 95% confidence intervals (95%CIs) for the association between postdiagnostic β-blocker exposure and overall or cancer-specific survival (OS and CSS, respectively). Adjustments were made for age at diagnosis, year of diagnosis, comorbidities, cancer stage, and cancer treatments.In our population of 6197 patients, 2373 patients (38%) had at least one prescription of β-blockers in the 5 years following diagnosis. Postdiagnostic exposure to β-blockers was associated with a significant decrease in OS (adjusted HR, 1.21; 95%CI 1.12;1.30; p < 0.001) and CSS (adjusted HR, 1.17; 95%CI 1.07;1.29; p < 0.001). Moreover, this association remained similar in dose-response analyses, in subgroup analyses (including by β-blocker selectivity types), and in sensitivity analyses.In this large nationwide cohort of ovarian cancer patients, β-blocker users had reduced survival.