We examined whether the extent of initial peritoneal dissemination affected the prognosis of patients with advanced ovarian, fallopian tube, and peritoneal carcinoma when initially disseminated lesions > 1 cm in diameter were removed, regardless of the timing of aggressive cytoreductive surgery. The extent of peritoneal dissemination was assessed by the peritoneal cancer index (PCI) at initial laparotomy in 186 consecutive patients with stage IIIC/IV. Sixty patients underwent primary debulking surgery and 109 patients underwent neoadjuvant chemotherapy followed by interval debulking surgery. Seventeen patients could not undergo debulking surgery because of disease progression during neoadjuvant chemotherapy. The median initial PCI were 17. Upper abdominal surgery and bowel resection were performed in 149 (80%) and 171 patients (92%), respectively. Residual disease ≤ 1 cm after surgery was achieved in 164 patients (89%). The initial PCI was not significantly associated with progression-free survival (PFS; p = 0.13) and overall survival (OS; p = 0.09). No residual disease and a high-complexity surgery significantly prolonged PFS (p < 0.01 and p = 0.02, respectively) and OS (p < 0.01 and p ≤ 0.01, respectively). The extent of initial peritoneal dissemination did not affect the prognosis when initially disseminated lesions > 1 cm were resected.