The asymmetric unit of the title compound, C(3)H(6)N(6).3C(8)H(5)NO(2), contains a melamine and a phthalimide [1H-isoindole-1,3(2H)-dione] molecule, both residing on a mirror plane, and a second phthalimide molecule residing on a general position. The two components are linked by almost linear N-H...O and N-H...N hydrogen bonds, forming an essentially planar superstructure. These aggregates, related by a twofold screw axis, interact through weak C-H...O contacts, forming chains parallel to the b axis, while those related by translation along the c axis interact via pi-pi interactions between the pi clouds of the aromatic triazine and phthalimide rings to form a stacked structure.