Juvenile white shrimp Litopenaeus vannamei (1.98 ± 0.28 g) were fed a commercial diet for 8 wk in triplicate to investigate growth and lipid metabolism at 3 salinities (3, 17, and 30). Shrimp weight gain and survival at 3 were significantly less than that at 17 and 30. No differences were found in whole-body proximate composition. Linolenic acid (18:3[n-3]) and (n-3) long-chain unsaturated fatty acid levels in the hepatopancreas, and n-3 long-chain polyunsaturated fatty acid level, especially eicosapentaenoic acid (EPA; C20:5[n-3]) and docosahexaenoic acid (DHA; C22:6[n-3]) in muscle at 3 were significantly greater than at other salinities. Fatty acid synthase, hormone sensitive lipase, lipoprotein lipase, adipose triacylglycerol lipase, acyl-CoA, diacylglycerol acyltransferase 2, elongase of very long-chain fatty acid 6, and Δ5 and Δ6 fatty acid desaturase activity was detected and showed a negative trend with an increase of salinity, and no significant differences were found among salinity groups (P > 0.05). The results indicate that the low salinity of 3 decreases the growth of L. vannamei. Although L. vannamei could not synthesize either DHA or EPA de novo, it possibly has the potential ability to convert linolenic acid to DHA and EPA regardless of salinity. However, the factors influencing this ability remain unknown and need further study.