Objective To evaluate the cost-effectiveness of a diagnostic laparoscopy prior to primary cytoreductive surgery to prevent futile primary cytoreductive surgery (i.e. leaving > 1 cm residual disease) in patients suspected of advanced stage ovarian cancer. Methods An economic analysis was conducted alongside a randomized controlled trial in which patients suspected of advanced stage ovarian cancer who qualified for primary cytoreductive surgery were randomized to either laparoscopy or primary cytoreductive surgery. Direct medical costs from a health care perspective over a 6-month time horizon were analyzed. Health outcomes were expressed in quality-adjusted life-years (QALYs) and utility was based on patient's response to the EQ-5D questionnaires. We primarily focused on direct medical costs based on Dutch standard prices. Results We studied 201 patients, of whom 102 were randomized to laparoscopy and 99 to primary cytoreductive surgery. No significant difference in QALYs (utility = 0.01; 95% CI 0.006 to 0.02) was observed. Laparoscopy reduced the number of futile laparotomies from 39% to 10%, while its costs were € 1400 per intervention, making the overall costs of both strategies comparable (difference € − 80 per patient (95% CI − 470 to 300)). Findings were consistent across various sensitivity analyses. Conclusion In patients with suspected advanced stage ovarian cancer, a diagnostic laparoscopy reduced the number of futile laparotomies, without increasing total direct medical health care costs, or adversely affecting complications or quality of life.