Abstract Background We estimated the predictive value of rectal (bSTI) pathogen detection for future HIV seroconversion among young adult sexual and gender minorities (YSGM) assigned male at birth (AMAB). Methods Data were collected between March 2018 and August 2022 from RADAR, a longitudinal cohort study of YSGM AMAB living in the Chicago metropolitan area (n=1,022). Rates of rectal bSTIs and the proportion of self-reported rectal bSTI symptoms are reported. We examined whether the presence of rectal bSTIs predicted HIV seroconversion using generalized estimating equations (GEE). Findings Participants tested reactive for rectal Mycoplasma genitalium (MGen), Neisseria gonorrhoeae (NG), and Chlamydia trachomatis (CT) at a rate of 20.8 (95% CI: 18.4–23.5), 6.5 (95% CI: 5.0–8.2), and 8.4 (95% CI: 6.8–10.3) cases per 100 persons, respectively. There were no statistically significant pairwise differences in self-reported rectal bSTI symptoms between participants with self-collected swabs testing non-reactive versus reactive for rectal MGen (χ2=0.04, p=.84), NG (χ2=0.45, p=.37), or CT (χ2=0.39, p=.46). In multivariate GEE analysis, rectal NG (AOR=5.11; 95% CI: 1.20 - 21.77) was a statistically significant predictor of HIV seroconversion after controlling for other bSTIs, demographics. and sexual risk behavior. Interpretation Our findings provide a robust longitudinal estimation of the relationship between primarily asymptomatic rectal NG nucleic acid detection and HIV infection. These findings highlight the importance of asymptomatic screening for bSTIs and targeting biobehavioral intervention to prevent HIV infection among YSGM with rectal bSTI agents detected.