Highly unsaturated fatty acids (HUFA) play a particularly important role in normal growth, immune function,and reproduction. In this study, the full-length cDNA of fatty acid elongase (ELOVL) from Chinese mitten crab (Eriocheirsinensis) was cloned for the first time using reverse transcription-polymerase chain reaction and rapid amplificationof cDNA ends analyses. The ELOVL cDNA sequence (GenBank accession number: KR005628) was 2089 bp long,with a 350-bp 5′-untranslated region (UTR), a 674-bp 3′-UTR, and an open reading frame of 1065 bp, including stopcodons that specified a protein of 354 amino acids. The presumed protein had a typical ELOVL structure with a diagnostichistidine box HVIHH motif, several conserved regions, and three putative transmembrane-spanning domains(KFTEFLDT, NTFVHIVMYVYY, and TNFQMI). The encoded protein shared 59% amino acid sequence identity withAcromyrmex echinatior (GenBank number: XP_011054336.1) and was clustered closely with Musca domestica andMarsupenaeus japonicus in a phylogenetic tree. The ELOVL gene was expressed in the hepatopancreas, intestine, muscle,stomach, heart, and gill. Higher levels were detected in the hepatopancreas and intestine (P<0.05) and lower levelswere observed in stomach, gill, cranial ganglia, muscle, thoracic ganglia, and the eyes, with trace levels expressed in theheart. We designed three different lipid-containing feeds and analyzed ELOVL mRNA expression in muscle, hepatopancreas,and gonads. The results showed the highest expression in the ovary after feeding for 98 days (P<0.05).ELOVL transcripts increased in the ovary and hepatopancreas with increased inclusion of SO in the diet, but no expressiondifferences were detected in muscle or testis. These results lay the foundation for further research into the mechanismsregulating E. sinensis HUFA biosynthesis.