The aim of this research was to evaluate the effects of including Miúda spineless cactus (Nopalea cochenillifera Salm Dyck) as a substitute for Tifton-85 hay (Cynodon dactylon) on the performance and carcass yield of lambs finished in confinement. An experiment was conducted with 24 Santa Inês lambs, with an average age of 119 ± 29.89 days and an average initial weight of 14.64 ± 2.28 kg. The animals were slaughtered after 89 days in confinement. Four diets were formulated, containing four inclusion levels of spineless cactus 0%, 6.5%, 16.63%, and 35.10 as a substitute for Tifton-85 hay. As the amount of spineless cactus in the diet increased, the lambs had higher dry matter consumption, water consumption, final weight, daily weight gain, feed efficiency, and body score. The diet with the highest inclusion of spineless cactus provided the highest gross margin. A level of 35.10% spineless cactus in the diet is recommended for the confinement of lambs.