Background: Informal caregivers often serve as decision makers for dependent or vulnerable individuals facing health care decisions. Decision regret is one of the most prevalent outcomes reported by informal caregivers who have made such decisions. Objective: To examine levels of decision regret and its predictors among informal caregivers who have made health-related decisions for a loved one. Data sources: We performed a systematic search of Embase, MEDLINE, Web of Science, and Google Scholar up to November 2018.