This study shows how the flow uniformity from a film die can be improved by modifying the die geometry using a 3D Computational Fluid Dynamics (CFD) optimization technique. In this study, various optimization strategies were used to optimize the geometry to meet the desired objectives of uniform flow at the die exit and minimal pressure drop. Finite element simulations using the numerically optimized geometry predict a more uniform flow than simulations using the baseline geometry. However, some of the numerically optimized die geometries obtained in this study would be impractical to fabricate. Thus we see the power of CFD-based optimization methods to lead towards potentially better performing options; but we also see the necessity of understanding both the die design technology and fabrication techniques in order to analyze the practicality of the proposed optimized solutions. This knowledge can be used to redirect the optimization towards more practical solutions through the use of geometric constraints. In addition, the effects of die temperature distribution and resin viscoelasticity on the flow uniformity in a film die were investigated. The magnitude of the thermal affects can be significant enough to mask other rheological effects. Computational Fluid Dynamics (CFD) simulations predictions using temperature-dependent viscosity models and gradients in the die wall temperature boundary conditions agreed well with the experimental measurements of flow uniformity. When the die wall is more uniformly heated, the flow uniformity is improved in both the measurements and simulations, although the simulations showed more deviation from the experimental results as the elasticity and shear thinning of the resins increased.