A novel and effective Slotted Pentagonal Adjacent Structure (SPAS) pair based Ultra Wideband (UWB) Multiple-Input Multiple-Output (MIMO) antenna is presented in this research paper. The proposed antenna with a compact size of 0.25 λ0 × 0.50 λ0 mm2 consists of a two slotted pentagonal patch element along with ground plane alteration (GPA). Four hexagonal metallic rings with opposite split orientation are embedded in the patch elements to achieve three notch bands. This proposed loop-based split ring resonator (SRR) design focuses on miniaturization or compactness while maintaining effective notch performance. According to the experimental results, the suggested UWB MIMO antenna's impedance bandwidth ranges from 4.0 GHz to 40.25 GHz cover with triple notch bands IEEE INSAT extended C-band (6.05 GHz to 7.16 GHz), X-band (8.9 GHz to 10.28 GHz) and K-band (24.65 GHz to 26.95 GHz). High isolation of > 24 dB is achieved by integrating a parasitic strip with ‘O’ shaped SRR slot in between the radiating elements. The fabricated compact antenna has good radiation patterns, high gain, TARC < −10 dB, high efficiency and low envelope correlation coefficient which is suitable for advanced wireless communications.