Objective: To identify the relationship between self-efficacy in sexual communication and condom use in sexually active adolescents aged 12 to 19 years. Specific objectives: 1) to describe the relationship between personal factors (sex, age, initiation of sexually active life, type and number of sexual partners) and self-efficacy in sexual communication, and 2) to identify the relationship between personal factors and condom use. Materials and methods: Descriptive correlational study with 102 sexually active students aged 12 to 19. A personal data form, the Sexual Communication Self-Efficacy Scale, and the Condom Use Scale (which measures frequency and consistency) with acceptable psychometric characteristics were administered. For statistical analysis, Chi-square tests (χ²) and Spearman correlations (rs) were used, with a confidence interval of 95%. Results: A relationship was found between the contraceptive communication subscale and consistency of condom use (rs=.200, p=.043). Age had a relationship with self-efficacy in sexual communication (rs=.287, p=.003) and three of its dimensions: sexual history (rs=.351, p=.001, condom negotiation (rs=.222, p=.025), negative sexual messages (rs=.307, p=.002). Age (rs=.396, p=.010) and number of casual partners (rs=.508, p=.001) were predictors of condom use. Conclusions: Although self-efficacy in sexual communication is a key factor in condom use, the descriptive results revealed that approximately half of adolescents did not use condoms during their last sexual encounter (frequency) or in the last 30 days (consistency). Keywords: Adolescent; Sexuality; Self Efficacy; Communication; Condoms.