This study aimed to compare the enrichment capacity of polyunsaturated fatty acids (PUFA) and the long chain polyunsaturated fatty acids (LC-PUFA) of two dipteran species, Hermetia illucens - black soldier fly (BSF) - and a blowfly, Chrysomya putoria (CP), and to test its influence on growth, digestive activities and immune responses of Nile tilapia. Two types of enriched insect larval meal were produced using larvae cultured either on vegetable substrates (VGS) to formulate two diets rich in linolenic acid (ALA) (BSF/VGD and CP/VGD), or on fish offal substrates (FOS), in order to produce two diets rich in ALA and eicosapentaenoic acid (EPA) (BSF/FOD) or in ALA + EPA and docosahexaenoic acid (DHA) (CP/FOD). These four insect-based diets containing only palm oil as a lipid source were compared to a control diet based on fish meal (FM) and fish oil (FO). After 60 days of feeding, ALA or DHA muscle content of fish fed BSF/VGD or CP/FOD diet was comparable to that of the FMFO diet, and all insect diets increased the EPA muscle levels, except for a reduction by the BSF/VGD one. The CP/FOD diet induced similar fish growth, feed efficiency and protein efficiency ratio compared to the control FMFO diet, while a decrease was observed in fish fed other insect diets. Only BSF/VGD led to a decrease in protein and lipid digestibility. CP or BSF larval meal significantly increased alkaline phosphatase activity regardless of fatty acid (FA) enrichment. The expression level of fads2, fads6 and elovl5 was significantly higher in fish fed the BSF/VGD diet compared to fish fed the FMFO diet. FA-enriched insect diets increased some immune variables such as lysozyme, peroxidase and ACH50 values of fish fed CP/FOD, CP/VGD or BSF/VGD diets. Moreover, the expression level of β-defensin-1 and mhcII genes were significantly higher in fish fed the BSF/FOD diet than the FMFO diet. Also, the expression of the pro-inflammatory gene il-1-β was significantly higher in fish fed FMFO diet than in those fed CP/FOD diet, but comparable to fish fed all other diets. No significant effects were observed for the other tested genes. The results showed a better efficiency in LC-PUFA enrichment of the CP larvae compared to BSF ones, resulting in a higher stimulation of the fish nutrient utilization processes and therefore, a higher growth capacity. Nonetheless, all dipteran larval meal stimulated the immune status whatever the insect species or dietary essential fatty acids.