This study hypothesized that the signal grass (Urochloa decumbens [Stapf] R. Webster) modifies its structural and productive characteristics under a silvopasture system with legume trees. The treatments were composed of (i) signal grass in monoculture and (ii) a silvopasture system intercropping signal grass + Mimosa caesalpiniifolia Benth. a legume tree, over two consecutive years. The experiment was set in a completely randomized block design with three replications. Grazing was carried out by cattle with an average body weight (BW) of 186 ± 26 kg. The type of system had no significant effect on the structural and productive characteristics of signal grass. In the first grazing season, the greatest canopy height (54 cm) and total forage mass (6473 kg DM/ha) occurred in the dry period. The leaf:stem ratio was greater in the rainy season. Forage accumulation (515 kg DM/ha/28 days) and forage accumulation rate (18 kg DM/ha/day) were greater in the rainy season. Higher total forage production (4583 kg DM/ha) occurred in the first grazing season. The silvopasture with double rows spaced 25 m apart and with a tree density of 600 plants/ha did not compromise the structural and productivity characteristics of the signal grass pasture. The legume M. caesalpiniifolia has the potential for use as an arboreal component in silvopasture systems with signal grass.