This study uses data from a representative sample of sexually active adults in urban Mozambique to examine the effectiveness of the JeitO condom social marketing (CSM) project in increasing condom use among men and women at risk of contracting HIV. More specifically, this study tests the hypothesis that exposure to programme interventions (communications and access) increases condom use with non-regular partners. Exposure to the CSM programme is high, and multivariate analyses show that exposure to CSM advertising and communications and knowledge of a condom source are associated with higher reports of condom use with non-regular partners. Analyses of regional differences in condom use show that knowledge and use of condoms with non-regular partners are higher than the national average in all four provinces where the CSM project has been operating for longer (18 months vs. 6 months). Multivariate analyses show that the above-average level of condom use in the capital, Maputo, can be attributed to the higher socioeconomic status of this population, but the above-average level of condom use among men and women in Sofala and Manica provinces is due, in part, to their high level of exposure to the CSM programme. These findings indicate that the JeitO CSM project's behaviour-change communications and condom distribution are effective in encouraging safer sex practices among persons engaged in sex with non-regular partners.