The study was carried out to evaluate the effect of inclusion of sodium bicarbonate (SB) in diets based on ground corn without forage for feedlot lambs. Twenty-eight ram lambs (Dorper x Santa Inês), with initial body weight of 30.2 ± 4.5 kg and 94 ± 8.4 days old were used. They were assigned to a randomized complete block design. Experimental diets were positive control, diet without forage containing soybeans hulls replacing ground flint corn in 400g/kg of dry matter (DM) (CONT); and three diets without forage based on ground flint corn containing 10 (10SB), 20 (20SB) or 30 (30SB) g/kg DM of SB. The inclusion of SB quadratically increased final body weight (P = 0.02), dry matter intake (DMI; P < 0.01), average daily gain (P < 0.01), feed eficiency (P < 0.01), slaughter body weight (P = 0.02), hot and cold carcass weight (P = 0.02), loin muscle area (P = 0.05), leg compacity index (P = 0.05) and the weights of: neck (P = 0.01), shoulder (P = 0.02), rib (P = 0.03) and leg (P = 0.01), with higher values for the 20SB. Feeding SB linearly decreased the area (P < 0.01) and height (P = 0.01) of the papillae. The use of SB improved the performance and increased hot and cold carcass weights, with better results observed in the 20 g/kg level (20SB), showing to be efficient in diets without forage for feedlot lambs.