The study aimed to evaluate the effect of three feeding systems on the productive performance and carcass fatty acid profile in Guinea pigs. Eighteen 21-day old male Guinea pigs were randomly distributed into three groups and housed in galvanized cages. The treatments were: T1, green alfalfa; T2, mixed feeding (concentrate feed + green alfalfa [10% BW]); T3, integral feeding (only concentrate feed). Weight gain, feed intake and feed conversion were measured weekly. On day 28 all animals were slaughtered to assess carcass yield. Total fat was extracted to determine the fatty acid profile by gas chromatography. The productive performance and fatty acid profile of the carcass of experimental animals were significantly influenced by the dietary treatments (p<0.05). T2 y T3 had higher daily gain weight, feed intake, carcass yield and lower feed conversion than T1; however, carcasses had higher content of omega-3 in particular α-linolenic fatty acid and lower content of omega-6, resulting in a lower n-6/n-3 fatty acid ratio and the lowest carcass fat content. It is concluded that alfalfa (Medicago sativa) is a source of n- 3 fatty acids, particularly α-linolenic acid, which can improve fatty acids n-3 content of Guinea pig carcasses.