AbstractBackgroundDecisional regret during or after medical treatments is linked to significant distress. Regret affects not only patients but also caregivers having an active or passive role during decision making. The Decision Regret Scale (DRS) is a self‐report measure for regret in patients after treatment decisions. However, practical and psychometrically robust instruments assessing regret in caregivers are lacking.ObjectiveTo develop and validate a caregiver version of the DRS (Decision Regret Scale for Caregivers [DRS‐C]).DesignPsychometric validation based on a web survey.Setting and participants361 caregivers of deceased German people/patients with cancer.Main variables studiedBesides structural validity and test‐retest reliability, we evaluated measurement invariance accounting for gender, age and closeness of relationship, and tested hypotheses on convergent/discriminant validity.ResultsForty‐five per cent of all caregivers demonstrated decision regret. Confirmatory factor analyses strongly supported the unidimensional structure of the DRS‐C and pointed to strict invariance. The DRS‐C demonstrated very good internal consistency (α = 0.83, 95% CI [0.81, 0.86]) and test‐retest reliability (ICC [A,1] = 0.73, 95% CI [0.59, 0.83]) along with sound convergent/discriminant validity. Concerning responsiveness, DRS‐C scores remained stable over a 12‐week period in 83.3% of all caregivers. Receiver operating characteristic analysis yielded a cut point of 43 for the identification of significant decision regret (AUC = 0.62, 95% CI [0.56, 0.68]).Discussion and conclusionsThe lack of a gold standard instrument prevented us from examining the criterion validity and determining a minimally important difference. Nevertheless, the DRS‐C provides valid and reliable information regarding caregiver regret following medical decisions. Above all, it captures a crucial aspect of the treatment experience in caregivers.