In the title compound, C15H19N3O2, the piperazine ring adopts a chair conformation, with its N-C bonds in pseudo-equatorial orientations. The dihedral angle between the C atoms of the piperazine ring and the phthalamide ring system (r.m.s. deviaiton = 0.008 Å) is 89.30 (8)°. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds, generating a three-dimensional network and aromatic π-π inter-actions also occur [centroid-centroid distances = 3.556 (1)-3.716 (1) Å].