Introductionprediction and importance of severe postoperative complications after ovarian cancer surgery is a strong issue in patient selection and evaluation. Pre- and early peroperative predictors of severe 30-days postoperative complications (Clavien-Dindo class ≥3) after surgery for primary ovarian cancer are not fully established, neither their impact on patients’ survival. Materials and methodsA prospective observational study included 256 patients with primary ovarian cancer FIGO stages IIB-IV, operated during 2009–2018 in a primary or interval debulking surgery setting. Patient variables were analysed in relation to severe postoperative complications (Clavien-Dindo class ≥3) and overall survival. ResultsHigh-grade postoperative complications occurred in 24.2% patients. Class 3a complications were observed in 12.5% cases. High-grade complications class ≥3 were observed in 31.6% after primary debulking surgery compared to 12.2% after interval debulking surgery (p = 0.0004). Peritoneal cancer index ≥21 and preoperative albumin concentration ≤33 g/L were independent predictors of high-grade complications. Peritoneal cancer index correlated with the surgical complexity score and completeness of cytoreduction. Increased peritoneal cancer index was a negative predictor of overall survival, but high-grade complications did not influence survival negatively. ConclusionsPeritoneal cancer index ≥21 was an independent predictor of high-grade complications after ovarian cancer surgery. Increased peritoneal cancer index also impacted overall survival negatively, but high-grade complications did not influence overall survival.