In this study, two Sxl gene homologs, designated as Mnsxl1 and Mnsxl2, were cloned and characterized from the freshwater prawn Macrobrachium nipponense by rapid amplification of cDNA ends. The deduced amino acid sequences of Mnsxl1 and Mnsxl2 showed high sequence homology to the insect Sxl and contained conserved domains in two RNA-binding motifs. Real-time quantitative reverse transcription-polymerase chain reaction (RT-QPCR) showed that the Mnsxl1 and Mnsxl2 genes were expressed in all investigated tissues, with the highest level of expression in the intestine and liver. RT-QPCR also revealed that Mnsxl1 and Mnsxl2 mRNAs expressions were both significantly increased at 5 and 20 days post-larvae after metamorphosis. Thus, the results of the present study imply that Mnsxl1 and Mnsxl2 playcomplex and important roles in the sex differentiation of M. nipponense.