Decision making regarding adjuvant therapy for high-risk endometrial cancer is complex. The aim of this study was to determine patients' and clinicians' minimally desired survival benefit to choose chemoradiotherapy over radiotherapy alone. Moreover, influencing factors and importance of positive and negative treatment effects (i.e. attribute) were investigated.Patients with high-risk endometrial cancer treated with adjuvant pelvic radiotherapy with or without chemotherapy and multidisciplinary gynaecologic oncology clinicians completed a trade-off questionnaire based on PORTEC-3 trial data.In total, 171 patients and 63 clinicians completed the questionnaire. Median minimally desired benefit to make chemoradiotherapy worthwhile was significantly higher for patients versus clinicians (10% vs 5%, p = 0.02). Both patients and clinicians rated survival benefit most important during decision making, followed by long-term symptoms. Older patients (OR 0.92 [95%CI 0.87-0.97]; p = 0.003) with comorbidity (OR 0.34 [95% CI 0.12-0.89]; p = 0.035) had lower preference for chemoradiotherapy, while patients with better numeracy skills (OR 1.2 [95%CI 1.05-1.36], p = 0.011) and chemoradiotherapy history (OR 25.0 [95%CI 8.8-91.7]; p < 0.001) had higher preference for chemoradiotherapy.There is a considerable difference in minimally desired survival benefit of chemoradiotherapy in high-risk endometrial cancer among and between patients and clinicians. Overall, endometrial cancer patients needed higher benefits than clinicians before preferring chemoradiotherapy.