Abstract Background Syphilis rates in the United States have increased. Few studies have examined syphilis incidence and prevalence prospectively among young sexual and gender minorities (YSGM). Methods This study of YSGM assigned male at birth comes from a Chicago-based prospective cohort at 2 visits 6 months apart (N = 882). Syphilis cases were identified through serologic test results and self-reported history. Results In this sample, 25.1% had a lifetime prevalence, and 3.3% were incident cases with a crude incidence rate of 6.76 per 100 person-years. Conclusions Lifetime syphilis and incidence are high in this sample of YSGM relative to general population samples. Syphilis rates have increased in the United States, particularly among young sexual and gender minorities. Few studies have examined syphilis longitudinally among sexual and gender minorities. Based on a prospective longitudinal design, this study found a lifetime prevalence of 25.1% and an incident case rate of 3.3% at 6-month follow-up.