The effect of a graft copolymer based on cellulose (CE) and polyacrylonitrile (PAN) on the compatibility of the two homopolymers in solution was analysed. Samples of copolymers containing different proportions of CE and PAN were synthesized. In order to reduce the degradation of the cellulose chain we tested different synthetic routes. After extraction of PAN homopolymer, the reaction products were composed of pure CE and copolymer; the percentage of PAN with respect to the total weight varied between 13 and 32.2%. A significant increase in compatibility was obtained by using graft copolymers in mixtures with the homopolymers, as evident from both ternary phase diagrams and morphology of solution-cast films. Moreover, solutions containing the graft copolymer showed a liquid crystalline phase at high concentration.