Background and objective Treatment for gynecological malignancies is complex and may cause unintended or accidental adverse events (AE). We evaluated the costs of hospitalization associated with those AEs among patients who had an abdominal or laparoscopic procedure for proven or suspected gynecological cancer at a tertiary gynecological cancer center in Australia. Methods Data on AEs were prospectively collected and matched with cost data (AU$ 2008) from the hospital's clinical costing unit and linked to demographical, clinical and histopathological data. Total costs were adjusted for various clinical factors and estimated using log-transformed ordinary least squared regression. Back-transformation was achieved using smearing factors. From epidemiological data, we also estimated the costs of AEs Australia-wide and undertook scenario and probabilistic sensitivity analyses to investigate the potential cost impact of reducing AEs. Results A total of 369 patients had surgical procedures of which 95 patients (26%) had at least one AE. Patients with AEs incurred an extra AU$12,780 on average, adjusted for age, co-morbidities, ovarian cancer, major or minor complications, surgical complexity, presence of malignancy and abdominal surgery. Mean adjusted costs (95% CI) for patients with intra-operative, minor post-operative and major post-operative AEs were AU$40,746 (11,582-71,859) AU$18,459 (17,270-19,713) and AU$67,656 (5324-131,761), respectively. Up to an estimated AU$20.6 million/year could be saved if the AEs were reduced by 40%. Conclusion Adverse events are associated with significantly increased hospitalization costs and appropriate evidence-based interventions are justified to minimize AEs.