Adolescents residing in urban poor Accra face sexual and reproductive health challenges. Interventions to address them have not been entirely effective; thus, researching adolescents’ sexual self-concept (SSC) could strengthen our understanding of precursors to their sexual activity. For this study, a culturally appropriate scale is developed to measure the SSC of adolescents in urban poor Accra. Focus group discussions and content analysis generated items in the scale. Factor analyses techniques were used to develop sub-scales measuring different SSC dimensions. Three sub-scales, ‘sexual enthusiasm’, ‘sexual intrepidness’ and ‘sexual readiness’ were reliable SSC measures. Validity assessments found that sexually ready and enthusiastic youth were more likely to have engaged in coital, pre-coital and risky sexual behaviors. Also, as their sexual intrepidness and enthusiasm increased, adolescents had significantly worse mental health. These scales may provide an important step in understanding adolescent sexual behavior in the urban poor context and thus need further investigation.