DM domain genes are a group of transcription factors that are integral to sexual development and its evolution in metazoans. Their functions and regulatory mechanisms are not well understood in Malacostraca (crabs and crayfish) while these sex regulators have been widely identified in the past decade. In this study, theDmrtfamily was investigated in the decapod crab,Eriocheir sinensis. We find that most members of theEsDmrtfamily begin to enrich around the juvenile 1 stage. In reproductive organs,EsDsx1,EsDsx2,EsiDMYandEsiDmrt1ahighly express in the male-specific androgenic gland (AG), whileEsDmrt-like,EsDsx-like,EsDmrt11E, andEsiDmrt1bshow relatively high expression in testis. Also, we find the highly aberrant expression ofEsiDMYandEsiDmrt1ain the chimeric AG, strongly indicating their function in AG development. Moreover, RNA interference ofEsDsx1,EsiDMY, andEsiDmrt1aresults in a significant decrease in transcription of theInsulin-like androgenic hormone(IAG), respectively. Our findings suggest thatDmrtgenes inE. sinensisprimarily function in male sexual differentiation, especially in AG development. Besides, this study identifies two unique groups ofDmrtgenes in Malacostraca:DsxandiDmrt1. In MalacostracaDsx, we uncover a cryptic mutation in the eight zinc motif-specific residues, which were firmly believed to be invariant across theDmrtfamily. This mutation sets the MalacostracaDsxapart from all the otherDmrtgenes and implies a different way of transcriptional regulation. Genes from theiDmrt1group show phylogenetical limitation to the malacostracan species and underwent positive selection, suggesting their highly specialized gene function to this class. Based on these findings, we propose thatDsxandiDmrt1in Malacostraca have developed unique transcriptional regulation mechanisms to facilitate AG development. We hope that this study would contribute to our understandings of sexual development in Malacostraca and provide new insights into the evolutionary history of theDmrtfamily.