Evidence suggests a substantial burden of sexually transmitted infections (STIs) and high proportions of sexual behavior with no protective barriers in transmasculine and nonbinary individuals. However, research on this population's sexual health has been scarce, especially in the Latin American region. This study sought to determine the prevalence of self-reported STIs, and to explore correlates of use of protective barriers during sexual behavior among transmasculine and nonbinary individuals in Argentina. A sample of 304 participants responded to a questionnaire online to explore sociodemographic variables, history of HIV and other STIs, access to sexual and gender-affirming healthcare, and sexual behavior. Chi-square tests were calculated, and bivariate and multivariable logistic regression analyses were conducted to identify correlates of use of protective barriers during sexual behavior. Almost a quarter (23.4%) self-reported lifetime diagnosis of at least one STI and 63.8% did not use any protective barriers in their last sexual relation. Use of protective barriers during sexual behavior was negatively associated with insertive frontal/genital sexual behavior and with sex with cisgender women in the last month, and positively associated with ever attending a gynecologic examination, sex with cisgender men in the last month and lifetime transactional sex. Only these last two variables remained associated with use of protective barriers in the multivariable model. Use of protective barriers differs by type of sexual behavior and partner in transmasculine and nonbinary people. Sexual healthcare targeting this community should take this into consideration, and preventive interventions should be tailored to each individual's self-reported sexual behaviors.