Using the General Social Survey (GSS) 2012, a national household-based probability sample of non-institutionalized U.S. adults, this study examined the association of social capital and sexual risk behaviors among older adults aged 55 years and older. Of the 547 respondents, 87% reported not using condoms during their last intercourse, and nearly 15% reported engaging in sexual risk behaviors, such as casual sex, paid sex, male to male sex, and drug use. Binary logistic regression results showed that age, gender, marital status, education, race, sexual orientation, and sexual frequencies were significant predictors of older adults’ unprotected sex. Social capital was not a predictor of unprotected sex but was positively associated with other human immunodeficiency virus/sexually transmitted disease (HIV/STD) risk behaviors such as sex with strangers, having multiple sex partners, injecting drugs, and having male to male sex. Findings of this study highlight the importance of HIV/STD prevention programs for older adults.