Abstract The meat production chain, while seeking to reduce production costs, has been demanding in terms of quality, with growing consumer concern regarding the benefits and harms that meat can bring to health. In this sense, the composition of ruminant fat has been a concern for the community in general, due to it being mostly composed of saturated fatty acids (SFA), Supplementary sources of polyunsaturated fatty acids (PUFA) in the diet of ruminants are being researched, especially long-chain ones, such as those present in some species of marine microalgae; however, these fatty acids are susceptible to oxidation, and the use of an antioxidant is recommended, like vitamin E. Given the above, the objective of this work was to evaluate the concentrations and relationships of fatty acids in the meat of Ile de France lambs fed with marine microalgae meal (Schizochytrium sp.) and vitamin E. Newly weaned (n = 32), 60-d-old, intact Ile de France breed lambs, with body weight (BW) = 20.0 kg were randomly distributed into four treatments: CO: control diet; FA: diet with 4% seaweed meal; VE: diet with 1,000 mg of vitamin E; or FAVE: diet with 4% seaweed meal and 1,000 mg of vitamin E. The lambs were slaughtered at 35 kg BW and their meat was evaluated regarding the fatty acid profile, to then obtain concentration and relationships of fatty acids in lamb meat. The data were evaluated in a completely randomized design, with four treatments and eight replications, with the means of the analysis of variance compared using the Tukey test, with 5% significance. A greater (P < 0.01) AGS and decreased AGI concentration were observed in the VE diet (51.47 and 48.53%, respectively), the greatest (P < 0.01) AGI and monounsaturated (AGMI) concentrations, were observed in the CO diet, with 53.63 and 45.14%, respectively. The concentration of PUFA in the FA treatment was greater (P < 0.01) in relation to the VE treatment and like the others (Table 1). The Σn–6 was greater in the CO treatment (7.44%) and less in the VE (4.22%), whereas the Σn–3 was 9.6 times greater (P < 0.01) in the FA treatment (4. 04%) in relation to CO (0.42%), the AVEF treatment exhibited the second greatest values (2.63%), followed by VE (0.49%). The n-6:n-3 ratio was 14 times less (P < 0.01) in the FA treatment (1.24) compared with CO (17.71), the second least value was in the FAVE (1.64), in the VE treatment, a ratio of 8.61 was observed. Seaweed flour from the genus Schizochytrium potentially increases concentration of n-3 in lamb meat and greatly reduces the n-6:n-3 ratio, resulting in a healthier food. Vitamin E, combined or not with a source of PUFA, does not bring benefits in terms of the fatty acid profile.