This study examined the relationship between sexual identities and perception of risks associated with illicit drug use among a nationally representative sample of US adults. We analyzed data from five waves of the National Survey on Drug Use and Health (NSDUH 2015-2019), with 205,418 adult participants. Six survey questions assessing participants’ perceptions of the risks associated with illicit drug use (LSD, heroin, and cocaine) were subjected to principal component analysis. Sex-stratified ordered logistic regressions were used to explore potential disparities in perceptions regarding the risk associated with illicit drug use among sexual minority identifiers. Among male participants, approximately 11.3% and 1.8% of them perceived illicit drug use as moderate and low risks, respectively. About 6.0% of female participants perceived illicit drug use as moderate risks, and 1.1% of female participants perceived it as low risk. The sex-stratified regression models demonstrated that participants who identified as lesbian/gay or bisexual all had higher odds of reporting low perception of illicit drug use risks as compared to their heterosexual counterparts (all p < 0.01). Illicit drug use prevention strategies should consider risk perception disparities by sexual minority populations.