The manuscript represents miniaturized two-radiating element-based MIMO antennas for the frequency span of 1 THz to 20 THz. Five MIMO antenna structures are designed and analysed by modifying the shape of radiating elements and ground regions to attain better performance. The proposed structures’ performance is compared in terms of return loss, isolation, total gain, directivity, radiation pattern, directivity, peak gain, ECC, TARC, CCL, and TARC. The presented design provides the minimum return loss of −50.85 dB, maximum isolation of 38 dB, maximum bandwidth (S11