The crystal structure of 4-(4'-ethoxyphenylazo)phenyl undecylenate has been determined by direct methods. The compound crystallizes in space group P21/n with a = 5.914(1), b = 15.143(3), c = 25.819(2)A° and β = 91.450(2)°. The structure was refined to R = 0.0412 for 1998 observed reflections. The molecule is almost linear and planar. The angle between the two phenyl rings is 3.996°. The pairs of molecules related by a centre of symmetry form an imbricated arrangement.