In this study, films from cassava starch and rosemary oil were prepared by using the casting method. Glycerol was used as plasticizer and tween 80 as surfactant. The influence of Cassava starch (Cs), Rosemary oil (Ro), Surfactant (Sf) concentrations and Thickness of film (Tf) on the mechanical, optical, and barrier properties of cassava starch films was studied applying the Response Surface Methodology. The response variables were optimized by using second order polynomial models with satisfactory fit and coefficient of determination (R 2 ) values (> 81%). The optimized conditions with the goal of maximizing mechanical properties and minimizing barrier and optical properties and desirability function (0.9796) were Cs = 3 g/100 g solution, Ro = 4 g/100 g Cs, Sf = 69 g/100 g Ro and Tf = 0.05 ± 0.001 mm. The films produced under these conditions displayed high mechanical strength (16.7 MPa), young´s modulus (2911.4 MPa), low elongation at break (0.2%), low water vapor transmission (0.8 × 10 −14 g/Pa s m), low solubility (33.24%), and low opacity (16%). These results provided good mechanical, barrier, and optical properties, compared to films based on other starch resources.