The title compound 1,5-diphenyl-3-phenacylthio-1H-1,2,4-triazole 2 (C22H17- N3OS, Mr = 371.45) was prepared by the reaction of 1-benzoyl-3-phenyl-aminothiourea 1 with 2-bromoacetophenone. The crystal is of triclinic, space group P1, a = 8.906(3), b = 9.853(3), c = 11.226(4) ?, α = 100.562(5), β = 101.285(5), γ =? 105.096(6)o, Z = 2, V = 903.7(5) ?3, Dc = 1.365 g/cm3, μ(MoKα) = 0.196 mm-1, F(000) = 388, the final R = 0.0506 and wR = 0.0985 for 2532 observed reflections (I > 2σ(I)). Its formation mechanism was proposed.