This study aimed to evaluate the effects of dietary condensed tannins (CT) from Acacia mearnsii extract on performance, carcass traits and meat quality of lambs. Forty uncastrated Santa Ines crossbreed lambs were randomly distributed in five diets with 0, 20, 40 and 60 and 80 g CT/kg DM inclusion. The CT inclusion from Acacia mearnsii extract in the diet of lambs quadratically increased (P < 0.05) DM intake, growth rate, lipid content and pH meat, and linearly reduced carcass weight and traits, commercial cut weights, color parameters (a*, b*, C*), fatty acids C16:1, C18:1, ∑MUFA, and meat softness. However, there were trend to linear increases on moisture (P = 0.061), shear force (p = 0.089), and linear increasing (P <0.05) on the luminosity (L*) color index, fatty acids C12:0, C18:0, C18:2, C18:3, C20:4, C20:5, C22:5, ∑PUFA, ∑odd chain FA, the ∑PUFA: ∑SFA ratio. Linear Response Plateau (LRP) analysis demonstrated that the inclusion at levels 0, 20 and 40 g CT/kg DM in lamb diet presented similar (P > 0.05) and were better that inclusion of 60 and 80 g CT/kg DM. The CT inclusion did not affect (P > 0.05) protein and ash meta concentration, water holding capacity, C14:0, C18:2cis-9-trans-11, and ∑UFA, ∑SFA: ∑UFA and ∑n-6:∑n-3 ratio. The inclusion of CT from Acacia mearnsii extract in the lamb diet did not affect (P > 0.05) the flavor or overall acceptability of the lamb meat. The LRP analysis demonstrated that the inclusion level 20 g CT/kg DM in lamb diet proportioned greater softness according panelists (P <0.001) compared others treatment. Condensed tannin from Acacia mearnsii extract can be used until a level of 20 g/kg DM since improved DMI, slaughter weight and two of the most profitable commercial cuts (loin and rib). In addition, it improved PUFA composition and softness of lamb meat. We don't recommend CT addition above 40 g/kg DM, as it may compromise sensory meat characteristics.