This work investigates the effect of antenna polarization in evaluating the performance of multiple-input multiple-output (MIMO) systems for enhancing the channel capacity. The evaluation is performed by computing envelope correlation coefficient (ECC) of established 2×2 MIMO antennas, using the scattering parameters as the analysis data. The 3.5 GHz 2×2 MIMO antennas with specific polarization types are used to accomplish the objectives of work. The results of investigation show that the proposed 2 × 2 MIMO antennas produces exceptional performance in terms of ECC. The value of ECC computed based on simulated and measured S-parameter data is coincided and has strong correlation one each other. An extension on separation between the elements of MIMO antenna considerably enhances the ECC value. In addition, circularly polarized MIMO antennas demonstrate a better ECC value in comparison to linearly polarized ones.