The title compound, C18H21BrN2O, crystallizes with two molecules (A and B) in the asymmetric unit (Z′ = 2). The major differences between the two molecules are related to the conformations adopted by their n-butyl side chains. The phenyl rings in both molecules are almost perpendicular, making dihedral angles of 79.2 (3) and 80.8 (3)°. The amide units are planar (r.m.s. deviations of 0.0018 and 0.021 Å) and almost perpendicular to the phenyl rings to which they are attached [dihedral angles of 68.9 (4) and 71.1 (4)°]. In the crystal, molecules A and B each form only an intermolecular N—H⋯O hydrogen bond with an adjacent molecule of the same kind. There are no significant intermolecular interactions between molecules A and B.