This study aimed to evaluate barbatimão bark extracts as a feed additive and substitute for lasalocid sodium (LAS) for feedlot lambs. Lambs were distributed into three treatments: LAS (0.018 g of lasalocid sodium), DBB (1.500 g of dried and milled barbatimão bark), and BHE (0.300 g of barbatimão hydroalcoholic extract). There was no effect (p = 0.32) of the inclusion of DBB and BHE extracts on the average daily gain. Inclusion of BHE in lamb diets reduced (p < 0.05) the fatness score compared to LAS, which was similar to DBB. The BHE decreased the yellowness intensity and hue angle (p < 0.05) of meat compared to the LAS. Animals that consumed DBB and BHE had a reduced (p = 0.04) total cholesterol level. Thus, the use of barbatimão bark extracts can replace lasalocid sodium in the diet of feedlot lambs, with no detrimental effects on performance or metabolic parameters.