Objective: Surgical assessment of residual tumor provides the strongest prognostic information in advanced ovarian cancer (AOC), with the best outcome observed after complete resection. Postoperative radiological assessment before initiation of chemotherapy can supplement the information obtained by surgical assessment; however, it may also reveal conflicting findings. Methods: Patients with AOC enrolled in the AGO-OVAR 12 trial underwent baseline imaging before the first chemotherapy cycle. The findings from surgical and radiologic assessment for disease extend were compared. Additionally, an integrated approach was assessed. Results: Complete data from all 3 assessment methods were available for 1345 patients. Of 689 patients with complete resection, tumor was observed in 28% and 22% of patients undergoing radiologic and integrated assessment, respectively. Patients with surgical- radiological and surgical-integrated concordant findings showed a 5-year overall survival (5Y-OS) of 72% and 71%, whereas patients with surgical-radiological and surgical-integrated discordant results showed inferior 5Y-OS of 47% and 49%, respectively. Patients with surgically assessed residual disease had a 5-YOS of 37%. The interval between surgery and baseline assessment was independently associated with discordance between assessment methods, which might reflect early tumor regrowth. Conclusions: Baseline tumor assessment before chemotherapy provides information that stratifies patients with complete resection into different prognostic groups. Integrating the data from different assessment methods might lead to improved definitions of prognostic groups. Further investigation to determine if earlier initiation of chemotherapy after debulking surgery could increase survival of patients with early tumor regrowth is warranted.