Abstract: Ocean acidification is known for a shift in the carbonate chemistry and a decrease in the pH of marine water due to increasing amounts of atmospheric carbon dioxide released from anthropogenic activities. Ocean acidification has a multiple effect on crabs from the phenotypic to molecular level. The present article first summarizes the effects of ocean acidification on the growth, development, physiology, metabolism, phenotype, and behavior of a variety of marine crab species. Furthermore, the mechanisms underlying the effects of ocean acidification on crabs are reviewed. Finally, suggestions and future research directions on controlling ocean acidification and its impact on crabs are presented.