tCellulose acetate (CA) plasticized by 1-butyl-3-methylimidazolium chloride (BMIMCl) and withdiethylphtalate (DEP) was obtained by melt processing at 150◦C. The effect and the interaction of ionicliquid with the cellulose acetate and their influence on structural, thermo-mechanical, rheological andtensile properties of CA materials were investigated.Ionic liquid (BMIMCl) has shown a good plasticization and more efficient destruction of the crystallinestructure of cellulose acetate than the DEP plasticized CA. BMIMCl interacts intensively with CA moleculesdue to the pronounced van der Waals interactions, hydrogen bonding and electrostatic nature of ionicliquid. The tensile test and the low Young’s modulus for plasticized CA suggest a strong reduction of theinteraction between the CA chains due to the presence of the ionic liquid.