Sexual health communication in adolescence is important for sexual well-being. With limited empirical work utilizing longitudinal methodologies, this study aimed to investigate how the frequency of sexual communication with parents, peers, and dating partners changes across adolescence and varies based on sex, race/ethnicity, and sexual orientation. Participants included 886 U.S. adolescents (54.4% females; 45.9% White, 22.6% Hispanic/Latinx, 21.6% Black/African American) surveyed yearly from middle school through 12th grade. Growth curve models were used to estimate trajectories of the frequency in communication. Results showed curvilinear trajectories for adolescents' sexual communication with their parents, best friends, and dating partners over time. Although all three trajectories showed curvilinear patterns, sexual communication with parents and best friends increased earlier in adolescence and leveled off, while sexual communication with dating partners was lower in early adolescence and showed a steep increase across adolescence. Communication trajectories significantly diverged depending on adolescents' sex and race/ethnicity but not their sexual orientation. This study provides the first evidence of developmental changes over time in adolescent sexual communication with parents, best friends, and dating partners. Developmental implications for adolescents' sexual decision making are discussed.