Large-scale anthropogenic mangroves have been constructed in coastal regions worldwide but our understanding of their ecological effects is limited. In particular, the question of whether and how anthropogenic mangroves influence biodiversity patterns remains elusive. Here, we investigated the influence of large-scale anthropogenic mangroves on biodiversity patterns of mangrove macrobenthos. Specifically, we measure and seek to explain differences in species richness, abundance, assemblage composition and distance-decay effect before and after the construction of anthropogenic mangroves. We surveyed assemblages of gastropod, bivalve and crab species over a wide latitudinal extent (24–28°N) in subtropical China. For each, we calculated species richness, abundance, assemblage composition and distance-decay relationship before and after the construction of anthropogenic mangroves. After the large-scale anthropogenic mangroves, we found species richness of gastropods, bivalves and crabs increased by 23.81%, 100% and 20%, respectively. The distance-decay effects of gastropods and bivalves decreased by 25% and 91.43%, while that of crabs remained virtually unchanged, which mediated by increased dispersal rate of macrobenthos. With mangrove plantation, compositional similarity of crab and bivalve assemblages increased by 28.57% and 38.46%, suggesting that large-scale monospecific planting exacerbate biotic homogenization. Altogether, these results indicate that large-scale anthropogenic habitats increase the diversity of mangrove macrobenthos and change taxonomic compositions by reducing distance-decay effects and increasing dispersal rate of macrobenthos. Synthesis and applications. We emphasize that afforestation of coastal wetlands can drive major changes in benthonic communities. Monitoring and assessing the ecological effects of the anthropogenic habitats for the presence of functional faunas will be important in determining the future coastal restoration and maintaining economic aquaculture. Quantifying those effects in terms of regional biodiversity composition will contribute to the management of coastal restoration to be based upon macroevidence rather than a one-sided local perspective.