Molecular and crystal structure of 4-[(p-N,N-dimethylamino)benzylidene]-2-phenyloxazol-5-one, C18H16N2O2, have been determined by single crystal X-ray diffraction study. The title compound is monoclinic, with a = 12.1704(23) , b = 3.9810(5) , c = 30.9603(56) , beta = 101.176(15)A degrees, Z = 4, D (x) = 1.32 g/cm(3), mu(Mo K alpha) = 0.087 mm(-1), and space group is P12(1)/c1. The structure was solved by direct methods and refined to a final R = 0.047 for 3166 reflections with I > 2 sigma(I). The crystal structure is stabilized by C-Ha <-O and C-Ha <-N type intra-molecular, C-Ha <-O type inter-molecular interactions. To enlighten the flexibility and the geometric isomerism (E or Z) of the title compound, the selected torsion angle is varied from -180 to 180A degrees in every 10A degrees separately and molecular energy profile is calculated and analyzed.