The patterns of distribution, abundance and reproduction of the Indo-Pacific barnacle Balanus amphitrite were surveyed at Costa do Sol mangrove, Maputo Bay, southern Mozambique using stratified sampling design. Balanus amphitrite exhibited a spatial variation in which high numbers of individuals colonized the upper stratum in comparison to the lower stratum. Seasonal abundance of B. amphitrite was greater in the upper stratum and declined in June and September. In contrast, very high densities of individuals were recorded in winter in the lower stratum. Gonad cycle showed continuous trend and release of embryos mainly took place in winter (May–July). There was a strong quadratic effect of temperature on breeding activity of B. amphitrite, with females continuing to brood at lower temperatures. Egg numbers increased linearly with female size. The success of the reproductive activity may be synchronized within the species, enhancing the establishment and colonization of B. amphitrite in the study area.