Background: Patients with advanced ovarian cancer have unfavorable prognosis after primary debulking surgery if the size of residual tumor exceeds 1 cm. The optimal approaches to systemic treatment of these patients remain unknown. We evaluated the efficacy and safety of dose-dose chemotherapy in frontline treatment of ovarian cancer patients after upfront non-optimal debulking surgery. Methods: This was a non-randomized single-arm phase II trial. We enrolled patients with advanced (FIGO III-IV) epithelial ovarian who underwent non-optimal upfront debulking surgery with residual tumor size > 10 mm. All patients were treated with dose-dense chemotherapy (ie, paclitaxel 80 mg/m² day 1, 8, 15 + carboplatin AUC6 day 1, cycled every 21 days – 6 cycles). Patients in historical control arm received standard chemotherapy with paclitaxel 175 mg/m2 day 1 + carboplatin AUC6 day 1, cycled every 21 days – 6 cycles. No patient in experimental or control arm received front-line bevacizumab or PARP inhibitors. The primary endpoint of the trial was progression-free survival (PFS). According to the historical data of our department, 1-year PFS in this category of patients equals to 51%. To increase 1-year PFS to 70%, 40 patients should be enrolled with α = 0.05 and β = 0.20 and estimated data loss for 10% of patients. Results: The study enrolled 40 patients to dose-dense chemotherapy arm, control arm included 86 patients. The trial arms were balanced in terms of age, performance status and other characteristics. Median follow-up was 28.8 months. The 1-year PFS was 76.9% compared to 51% in historical arm, median PFS was 19.8 months and 12 months respectively (HR 0.61; 95% CI 0.39-0.95; p = 0,03). The 1-year overall survival rate was 92.3% with median OS not reached with specified follow-up period. Severe neutropenia, anemia, thrombocytopenia was observed in 82.1%, 53.8%, 15.3% of patients, respectively. Conclusions: The results of the study showed high efficacy of dose-dose chemotherapy as front line of treatment for advanced ovarian cancer patients after non-optimal upfront debulking surgery but one should consider high toxicity of this regimen.