A study was conducted to evaluate the effects of dietary inclusion of black soldier fly (Hermetia illucens) larvae oil (HIO) on fillet fatty acid (FA) profiles and other nutritional traits of gilthead seabream (Sparus aurata). Four experimental diets were formulated with 45% crude protein and 18% lipids (circa 50:50 of fish oil and vegetable oil (VO) blend: 20% rapeseed, 30% palm, and 50% linseed oil) and HIO was used to replace VO blend at 42%, 84%, and 100%, corresponding to a dietary inclusion level of 4%, 7.9%, and 9.5%, respectively. After a feeding trial of 10 weeks, several fillet quality traits were analyzed, including morphometric and somatometric indexes, physical and chemical characteristics, FA profile, and lipid peroxidation products. No differences were found in the morphometric and somatometric parameters, or skin and fillet color. The fillets FA profile was significantly modulated by the experimental diets, showing an increase in saturated fatty acids (SFA), particularly lauric acid, and a decrease in monosaturated FA and n-3 and n-6 polyunsaturated fatty acids (PUFA) with the increase of HIO inclusion, while eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) contents were not affected. Fillets FA quality indexes (PUFA/SFA, n-3/n-6 PUFA ratio, hypocholesterolemic/hypercholesterolemic ratio, thrombogenicity, and atherogenicity indexes) were also modulated by dietary HIO inclusion. Fillets pH was reduced and water holding capacity increased with dietary HIO inclusion. Fillet lipid peroxidation level (measured as TBARS) was significantly decreased with dietary HIO inclusion despite an increase in conjugated dienes. Overall, results showed that HIO can efficiently replace VO in gilthead seabream diets, without major negative effects on fillet characteristics and quality traits while decreasing fillet lipid oxidation.