This paper presents an eight-element dual-band MIMO antenna array designed for 5G mobile phone applications, operating in the frequency bands of 3.37-3.61 GHz and 4.9-5.1 GHz. The antenna system is optimized for seamless integration into smartphones, offering high isolation and low ECC (Envelope Correlation Coefficient). The design features a modified T-shaped slot antenna array with elements measuring 20×11.8 mm², arranged symmetrically on the ground plane. A key design element is the inclusion of a decoupling section Dx between the antennas, which enhances isolation by managing surface currents. The antenna achieves isolation levels exceeding -14 dB, with ECC values below 0.05 in the lower band and 0.02 in the higher band. The antenna exhibits an efficiency range of 48.5% to 63.7%, a channel capacity of 38.8 bps/Hz, and a gain of 3.9 dBi, making it suitable for integration into smartphones and supporting next-generation mobile communication technologies. The design uses a low-cost FR-4 substrate and an L-shaped microstrip feedline, providing a cost-effective and efficient solution for 5G communication. The antenna's performance was validated through simulations and measurements, showing good agreement between simulated and measured results. The design also demonstrates robust performance in single and dual-hand modes, with minimal impact on isolation and efficiency due to user hand presence. The antenna's SAR (Specific Absorption Rate) levels were found to be within safe limits, ensuring user safety. The proposed antenna system is a promising candidate for 5G MIMO applications, offering high isolation, low ECC, and efficient performance.This paper presents an eight-element dual-band MIMO antenna array designed for 5G mobile phone applications, operating in the frequency bands of 3.37-3.61 GHz and 4.9-5.1 GHz. The antenna system is optimized for seamless integration into smartphones, offering high isolation and low ECC (Envelope Correlation Coefficient). The design features a modified T-shaped slot antenna array with elements measuring 20×11.8 mm², arranged symmetrically on the ground plane. A key design element is the inclusion of a decoupling section Dx between the antennas, which enhances isolation by managing surface currents. The antenna achieves isolation levels exceeding -14 dB, with ECC values below 0.05 in the lower band and 0.02 in the higher band. The antenna exhibits an efficiency range of 48.5% to 63.7%, a channel capacity of 38.8 bps/Hz, and a gain of 3.9 dBi, making it suitable for integration into smartphones and supporting next-generation mobile communication technologies. The design uses a low-cost FR-4 substrate and an L-shaped microstrip feedline, providing a cost-effective and efficient solution for 5G communication. The antenna's performance was validated through simulations and measurements, showing good agreement between simulated and measured results. The design also demonstrates robust performance in single and dual-hand modes, with minimal impact on isolation and efficiency due to user hand presence. The antenna's SAR (Specific Absorption Rate) levels were found to be within safe limits, ensuring user safety. The proposed antenna system is a promising candidate for 5G MIMO applications, offering high isolation, low ECC, and efficient performance.