Risky sexual behavior (RSB) during adolescence increases risk for sexually transmitted diseases, HIV/AIDs, and teenage pregnancy. Youth with externalizing disorders are more likely to engage in RSB, and antisocial traits in adolescence may be particularly relevant to RSB. It is still not clear which specific antisocial traits are most relevant to RSB and RSB attitudes, or how biological sex influences RSB and RSB attitudes in adolescence. The present study examined RSB and RSB attitudes, and their relationship with sex among inpatient adolescents with antisocial traits. 128 female and 52 male (N = 180) inpatient adolescents ranging from 12 to 17 years of age (M = 15.28, SD = 1.41) completed self-report measures of antisocial features, RSB, and RSB attitudes. Correlations, followed up with multiple linear regressions, were used to examine relations between antisocial features, adolescent age, RSB, and RSB attitudes. Results indicated no sex differences in RSB; however, significant sex differences in RSB attitudes were found. All antisocial facets, apart from stimulus seeking, were not related to RSB. Most antisocial facets were found to be related to RSB attitudes, most significantly antisocial behavior. Age at admission was the variable most significantly related to RSB and RSB attitudes. Results suggest that, for inpatient adolescents, antisocial features may not be related to engagement in RSB; however, the presence of riskier attitudes may affect future engagement in RSB among adolescent males with antisocial traits later in life and therefore present important preventative targets.