We examined the feasibility and acceptability of an HIV prevention intervention for African American adolescents delivered via mobile cell phones and looked at intervention-related changes in beliefs and sexual behaviors. We used a longitudinal one-group comparison design with data collected at three points. Forty adolescents, 13-18 years old, participated in the Becoming a Responsible Teen intervention followed by the delivery of daily multimedia messages for 3 months. The mobile-cell-phone enhanced intervention was feasible and acceptable to the participants. Greater HIV knowledge, improved attitudes toward condoms, and increased perceived HIV risk scores were observed with older adolescents (16-18 years old). Behavior trends showed a decrease in the number of times participants reported engaging in unprotected sexual intercourse over the previous 2 months. Mobile-cell-phone multimedia-text-messaging boosters tested in this study provided preliminary evidence of efficacy of the enhanced HIV prevention intervention for African American youth. © 2013 Association of Nurses in AIDS Care.