Handgun and gang violence represent two important threats to public safety. Although several studies have examined the factors that increase the risk for gang membership and handgun carrying, few studies have explored the biosocial underpinnings to the development of both gang involvement and carrying a handgun. The current study addressed this gap in the literature by using kinship data from the National Longitudinal Survey of Youth 1997 to estimate the genetic and environmental effects on gang membership, handgun carrying, and the covariance between the two. Results revealed that genetic and nonshared environmental influences accounted for much of the association between gang membership and handgun carrying. Implications of these findings for future gang research are discussed.