A new thiosemicarbzone compound was prepared by the reaction of acenaphthenequinone and thiosemicarbazide (1:1 molar ratio) in absolute methanol at 70°C. The crystal structure of this compound, acenaphthenequinone thiosemicarbazone mono methanol, was determined by X-ray crystallography. The unit cell parameters are as follows: a = 7.0384(14) Ǻ, b = 14.202(3) Ǻ, c = 14.270(3) Ǻ, β = 104.26(3)°. It crystallizes in a monoclinic system, with space group P2₁/c and four molecules in the unit cell. The final R value is 0.0738 for 2422 independent reflection.  Both inter and intramolecular hydrogen bonds exist in crystalline system.