Social and economic inequalities in condom use by adolescents have been reported previously. Also, condom use has declined during the last decade. The aim of the study was to describe trends in the use of condoms in our setting, and how these trends may differ between socioeconomic groups in boys, and separately in girls, aged 17-19 years attending school in Barcelona between 2004 and 2012. We analyzed data from three annual surveys on risk factors in secondary students, which included a representative sample of the city's population; individuals who had previously had sexual intercourse (n = 1570) were included in the study. We calculated adjusted prevalence ratios (aPR) and their confidence intervals (95 % CI) using robust Poisson regression models. The prevalence of condom use among boys was 87.0 % in 2004 and 76.2 % in 2012, and 76.7 and 64.7 % among girls, respectively. This decrease was greater in adolescents with a low socioeconomic level, both in boys (aPR = 0.80) and girls (aPR = 0.84). The observed increase of socioeconomic inequalities in condom use in adolescents highlights a possible deterioration in good sexual practices and policies during the studied period.