Transgender and nonbinary people experience substantial barriers to accessing healthcare, including prevention of HIV and other sexually transmitted infections (HIV/STI), due to structural inequities. We examined differences in insurance, HIV/STI prevalence, testing, and preexposure prophylaxis use among transgender and nonbinary people living in Washington State by race and ethnicity and gender. We pooled data from five 2019-2021 Washington State HIV/STI surveillance data sources to obtain a large and diverse sample of 1648 transgender and nonbinary participants. We calculated the risk difference (RD) for each outcome and used Poisson regression to estimate a surrogate measure of additive interaction-attributable proportion (AP)-that measures the proportion of the excess prevalence of the outcome observed at the intersection of gendered and racialized experience, beyond that expected from gender or race and ethnicity alone. Participants reported overall high levels of poverty (29% incomes <$15,000 and 7% unstable housing). Certain groups, especially racial/ethnic minority transgender women, were disproportionately impacted by HIV/STIs (RDs from 20% to 43% and APs from 50% to 85%) and less likely to currently have insurance (RDs from 25% to 39% and APs from 74% to 93%) than that expected based on gendered or racialized experience alone. Our findings highlight the heterogeneity in insurance access, HIV/STI positivity, and prevention utilization within transgender communities. We observed that a large proportion of increased HIV/STI prevalence among racial/ethnic minority transgender women was attributable to the intersection of gender and race and ethnicity. Our findings highlight the importance of trans-inclusive models of HIV/STI prevention that address multilevel barriers rooted in cissexism and structural racism.