Current research indicates a strong association between adverse childhood experiences (ACEs) and adverse health outcomes. Participants in frequently cited ACE research are predominantly heterosexual and cis gendered; the extent to which ACEs affect health outcomes among sexual and gender minorities (SGMs) is unclear. This systematic review examined the frequency of, and relationship between, ACEs and negative health outcomes among SGM. CINAHL, MEDLINE, PsycARTICLES, PsycINFO, Scopus, and PubMed databases were searched with no date restriction. After eliminating duplicates, titles and abstracts were reviewed resulting in 22 articles to be critiqued using the Joanna Briggs Institute Critical Appraisal Checklist for Analytical Cross-Sectional Studies. A total of 22 studies met final inclusion criteria. The frequency of reporting at least one ACE among SGMs ranged from 51.4 to 91.6%, while the frequency of reporting four or more ACEs ranged from 18.1 to 60.7%. SGMs reported a higher frequency of ACEs than non-SGM. ACEs were associated with poorer mental and physical health outcomes, as well as increased risky behavior among SGMs. SGMs report a high frequency of ACEs, but current studies did not include data regarding ongoing stigma and adversities that may further contribute to their negative health outcomes. Further research is needed to fully understand the impact of adversities experienced due to the sexual and/or gender orientation of this minority group.