The title compound 9-(4-dimethylaminophenyl)-1,8-dioxo-9H-dibenzo[c,h]- 2,7,10-trioxanthene (3) was synthesized by the reaction of 4-hydroxycoumarin with 4-dimethyla- minobenzaldehyde, and its chemical structure was determined by X-ray single-crystal diffraction. It crystallizes in triclinic, space group P1 with a = 7.8753(16), b = 11.029(2), c = 12.913(3) A, ct = 69.79(3), β= 89.01(3), γ = 81.90(3)°, V = 1041.5(4) A3, Z = 2, F(000) = 456, Dc = 1.395 Mg/m3, M,. = 437.43, μ= 0.097 mm-1, 2 = 0.71073 A, the final R = 0.0491 and wR = 0.1314 for 2662 observed reflections with I 〉 2σ(I).