Abstract: The title compound 4-Dimethylaminobenzaldehyde-4-amino-4H-1,2,4-triazole has been prepared by 4-amino-4H-1,2,4-triazole and 4-Dimethylaminobenzaldehyde with acetic acid as the catalyst. The chemical formula is C₁₁H₁₃N₅. The crystal structure was determined by single crystal X-ray diffraction. The crystal is monoclinic, space group P₂(1)/n with a= 10.365 5 (16), b= 11.158 5(19), c= 9.524 8 (12) ,  β= 90.257 0 (10)°, V= 1 101.8 (3)³, Z= 4, D_c = 1.298, F(000)=456, μ=0.084 mm^-1, R₁ = 0.079 0, wR₂ = 0.118 6 for 1183 observed reflections with I>2σ(I). Theoretical calculation based on density functional theory (DFT) for the title compound is also employed to predict and compare the experimental results, the geometrical structure and frontier orbital has been computed, and the quantum chemical calculation provides a good testimony for the crystal structure.