Synchrotron radiation was used to study the structure of the title compound, C(20)H(19)BrN(2)O(3).C(3)H(7)NO, which was obtained as fine fragile needle-shaped crystals by recrystallization from dimethylformamide (DMF), one molecule of which is incorporated per asymmetric unit into the crystal. The compound adopts a compact closed conformation with the orientation of the benzyl group such that the aryl ring is positioned over the piperazinedione ring, resulting in a C(spiro)...C(trans)-C-C(Ph) pseudo-torsion angle of -3.3 (3) degrees . The five-membered ring is present in an expected envelope conformation and the six-membered piperazinedione ring adopts a less puckered boat-like conformation. Reciprocal amide-to-amide hydrogen bonding between adjacent piperazinedione rings and C-H...O interactions involving DMF molecules propagate in the crystal as a thick ribbon in the a-axis direction.