The isolation of lectins from Myracrodruon urundeuva bark (MuBL) and heartwood (MuHL) as well as the termiticidal activity of MuHL against Nasutitermes corniger has already been described. This work reports on the purification of a leaf lectin (MuLL) and the characterization of MuBL, MuHL, and MuLL; also described are the resistance of hemagglutinating activity of the three lectins to trypsin activity from N. corniger gut and the termiticidal activity on N. corniger of MuBL (LC50 of 0.974 mg ml−1 on workers and 0.787 mg ml−1 on soldiers) and MuLL (LC50 of 0.374 mg ml−1 on workers and 0.432 mg ml−1 on soldiers). The antibacterial effect of MuBL, MuHL, and MuLL on bacteria from gut of N. corniger was also investigated and lectins showed similar bacteriostatic activity (MIC of 62.5 μg ml−1 for workers and 125 μg ml−1 for soldiers). MuBL and MuHL were more efficient bactericidal agents on bacteria in the workers’ gut (MBC of 125 μg ml−1) than MuLL (MBC of 250 μg ml−1) and similar bactericidal activity was detected on bacteria in the gut of soldiers (MBC of 250 μg ml−1). The termiticidal activity of M. urundeuva lectins can be explained by the chitin-binding property, resistance to termite digestive enzyme, and the antibacterial effect on symbiotic bacteria of N. corniger gut.