Beta agonists (BAA) are known for decreasing lipogenic activity and increasing lipolysis on beef and immunocastration (IM) could be an alternative tool to improve fat deposition. Therefore, this work was developed to evaluate the effect of BAA and IM on meat quality traits of feedlot finished Nellore cattle. Ninety-six bulls (409 ± 50 kg LW; 20 mo old) were divided into 2 groups and half of the bulls remaining bulls and the other half receiving 2 doses of IM vaccine (Bopriva) over a 30 d period before arrival at the feedlot. Cattle were fed for a period of 70 d on common diet (76% concentrate and 24% roughage). Each of these groups were then split in 3 groups and fed during 30 d one of the following treatments: control diet without BAA (CON); CON diet plus 80 mg/day zilpaterol hydrochloride (Zilmax; ZIL); CON diet plus 300 mg/day of ractopamine hydrochloride (Optaflexx; RAC). The cattle fed ZIL were 2 d withdrawal period before harvested. After 100 d on feed, cattle were harvested and one samples of LM was collected between 12/13th ribs for fatty acid profile determinations. Data was analyzed by ANOVA as randomized complete block (initial LW) design in 2 × 3 factorial arrangement and means were compared by Student t-test. There was no significant interaction of gender condition and BAA for any traits evaluated. Immunocastrated cattle had a greater percentage of MUFA (45.9 vs. 43.0; P = 0.002), palmitoleic (3.0 vs. 2.6; P = 0.002), Oleic (36.1 vs. 33.3; P = 0.002) and total Lipids (3.2 vs. 2.3 g; P = 0.002) compared with non-castrated, respectively, whereas non-castrated had greater stearic concentration (13.8 vs. 12.6; P = 0.006). Treatments CON and RAC showed greater values than ZIL for myristic (2.5 and 2.4 vs. 2.1; P = 0.017) and palmitic (23.7 and 23.0 vs. 21.9; P = 0.009), whereas ZIL treatment had greater values than CON and RAC for linoleic (8.5 vs. 6.7 and 6.5; P = 0.030), arachidic (2.6 vs. 1.8 and 1.8; P = 0.046), Omega 6 (12.1 vs. 9.2 and 9.4; P = 0.039). Beef from cattle fed ZIL presented greater CLA and PUFA concentrations, thus having more healthy beef. Immunocastrated cattle have more fat (lipids), MUFA and saturated fatty acids. Sex condition and BAA can be used to change the fatty acid profile of beef from Nellore cattle.