Knowledge of allelopathic interactions between grasses and legumes can contribute for the successful establishment of mixed tropical pastures in Brazil. The purpose of this work was to evaluate the allelopathic effect of the hydrolate and water decoction ofBrachiaria humidicola(Rendle) plant parts (root, shoot, and seeds) on four tropical forage legumesStylosanthesspp. cv. Campo Grande,Macrotyloma axillare, Calopogonium mucunoides, Desmodium ovalifolium, and on lettuce (Lactuca sativaL.), this last species used as a sensitivity standard in allelopathic bioassays. The results obtained for roots and shoots showed, in the case of hydrolate, the highest inhibitory effect on germination rates of the receiving species, while seed hydrolates had a stimulating effect depending on the legume species. In contrast, water decoction extracts had the highest inhibitory effects on root and seed fraction, and the lowest on the shoot fraction. Regarding the receiving species, germination percentages ofM. axillareshowed higher tolerance to inhibitory effects of the aqueous extracts ofB. humidicola, whileD. ovalifoliumshowed the highest sensitivity.