Sulfonated, block copolymers have traditionally been studied for applications in fuel cells and chemical protective clothing, among others. As such, most investigations have focused on the evaluation of transport properties and the selectivity and permeability of the polymer membranes. This work, however, focuses on the electrical characterization of sulfonated poly(styrene–isobutylene–styrene) (SIBS) triblock copolymer thin films. More specifically, the dielectric properties of SIBS are evaluated as a function of critical parameters such as frequency, sulfonation percent, and the polymer concentration. The results show that the dielectric constant increases with sulfonation percent and polymer concentration to values as high as 13,600. This work also provides insights into the correlation of SIBS electrical properties with its chemical structure and morphology. The structure–property relationship is derived through a combination of techniques including: elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and atomic force microscopy.