A hexagon shaped four-port ultra-wideband (UWB) MIMO antenna is proposed for WBAN application. The substrate used is Rogers 5870 which is flexible and biocompatible. The single antenna’s and MIMO antenna’s total layouts are 28 × 25× 0.76 cubic millimeter and 58 × 58× 0.76 cubic millimeter. The diversity parameters like ECC 9.6 dB, CCL< 0.2 bits/s/Hz and TARC <-12 dB are calculated. The proposed antenna's maximum gain and efficiency are 3.957 dBi and 98.5% respectively. To guarantee that the proposed antenna does not expose human tissues to radiation, a specific absorption rate (SAR) analysis is assisted. For 1 gram of tissue, SAR values of 0.513 W/Kg is obtained at 4 GHz and 0.316 W/kg is achieved at 8 GHz.