Adult trans women in Brazil are highly impacted by HIV, but little is known about risk for young trans women. Our study was conducted to compare the HIV prevalence and correlates of risk for young trans women ages 18-24 years old to adult trans women in Brazil. Trans women were recruited from Rio de Janeiro and Baixada (the metropolitan area of Rio de Janeiro), Brazil (N = 345). Youth ages 18-24 years of age had significantly greater odds of being HIV negative than adults (OR 0.4, 95% CI 0.2-0.6, p = 0.0002), but significantly lower odds of having post-exposure prophylaxis (PEP) knowledge (OR 0.5, 95% CI:0.3-0.9, p = 0.02) and PrEP awareness (OR 0.5, 95% CI: 0.3-0.8, p = 0.01). Young trans women also had significantly higher odds of using substances (OR 1.8, 95% CI 1.1-2.9, p = 0.02) and condomless anal intercourse with their last three sexual partners (OR 1.8, 95% CI: 1.1-3.0, p = 0.03) compared to adults. Already by age 24, one in four trans women in Brazil were infected with HIV pointing to a new generation at high risk of acquiring HIV. HIV prevention interventions are needed to change the healthcare system to reach and engage young trans women.