In this paper, a novel multiple slot loading technique is studied in detail for the isolation enhancement of the dual-band MIMO antenna system. The proposed MIMO antenna design consists of the microstrip patch loaded with T-shaped slots parallel to the non-radiating edge of the patch. The frequency tuning could be achieved by varying the length of the T-shape slot arm. The proposed MIMO antenna system is optimised for operation in WLAN and WiMAX applications. The isolation enhancement is achieved by providing simple multiple slots loaded in the ground plane between radiating elements. The length of the slots is λ/4. The system is fabricated and tested using a vector network analyser and anechoic chamber. The reduction in mutual coupling up to −29.16 dB and −24.09 dB for the 2.4 GHz and 3.4 GHz, respectively, is achieved. The bandwidths are 62.3 MHz (3.33–3.39 GHz) and 55.5 MHz (2.37–2.42 GHz), respectively. The total gain obtained in this case is 1.8 dBi at 2.4 GHz and 1.2 dBi at 3.4 GHz, respectively. The dimensions of the proposed designed antenna are 70 mm × 60 mm × 1.6 mm. The results were also verified through mutual coupling parameters like envelope correlation coefficient (ECC) and channel capacity loss (CCL) at the desired frequencies. © 2020 John Wiley & Sons, Ltd.