The influence of controlled biaxial uniform deformation of annealed and unannealed (with residual solvent) Ultem 1000 amorphous glassy polyetherimide films on their mechanical and gas separation characteristics have been studied. It has been shown that the transport and mechanical properties of strained Ultem-1000 film samples can be examined on reaching the quasi-steady state 48 hours after the beginning of their deformation. It has been shown that an increase in the strain of the unannealed Ultem 1000 films leads to an increase in mechanical strength of the films (increase in elastic modulus, tensile strength, and upper and lower yield stresses and decrease in elongation at break), an increase in chain packing density, and orientation of chains in the dense part of the polymer matrix, with these changes resulting in a drop of gas permeability and an enhancement of ideal selectivity. It has been demonstrated that the deformation of the annealed Ultem films leads to a dramatic change in mechanical properties even at small strains: from brittle fracture to the emergence of plastic deformation. As the strain increases, the gas diffusion coefficients decrease for all the samples, suggesting the ordering of chain packing. Thus, the combination of the methods used has made it possible to obtain information about the effects of deformation of polymer films and the residual solvent on their structural and transport properties useful for achieving the best permeability-selectivity ratio.