A quadruple band with L-slotted multiple-input-multiple-output (MIMO) square dielectric resonator antenna (SDRA) for fifth generation (5G) applications at the sub-6 GHz band is presented, which can cover 5G new radio band N77 (3.3–4.2) GHz and N79 (4.4–5) GHz. The proposed structure consists of a single SDRA mounted on a substrate excited by an aperture slot underneath dielectric resonators (DR)s. The performance of SDRA is improved by introducing L-shaped slot on the central part of DRA. Results show that the MIMO SDRA antenna achieves S11<-10 dB and S21<=-15 dB for all resonant frequencies at 3.5 GHz, 4 GHz, 4.6 GHz, and 5 GHz, indicating good performance of the antenna at the desired frequencies. The maximum realized gain is 5.61 dB and 5.01 dB at port 1, 4 GHz and port 2, 4.6 GHz, respectively. The radiation efficiencies are acceptable for all resonant frequencies. Moreover, the proposed antenna design achieved good envelop correlation coefficient (ECC) and diversity gain (DG) at the desired frequencies. Thus, the antenna can be used for 5G sub-6 GHz applications.