In polymers for an anti-reflective coating, compositions for an anti-reflective coating and methods of forming a pattern of a semiconductor device using the same, the compositions for an anti-reflective coating include a polymer that includes a first repeating unit having a basic side group, a second repeating unit having a light-absorbing group, and a third repeating unit having a cross-linkable group; a photoacid generator; a cross-linking agent; and a solvent. The polymer for the anti-reflective coating, which may have a basic side group chemically bound to a backbone of the polymer, may properly adjust diffusion of an acid in an anti-reflective coating layer to improve the profile of a pattern.