Self-decoupling coupled-fed patch antennas are designed in this letter. The self-decoupling mechanism is based on the weak-field region formed by the T-shaped probe feed and the radiating patch of the antenna element itself. When another identical antenna element is placed in the weak-field region, high isolation between the two elements can be achieved without adding extra decoupling structures. To validate the decoupling mechanism, a dual-element antenna array is initially built and an isolation level of better than 30 dB is achieved over the impedance band of 3.3–3.66 GHz with an element spacing of 0.53λ₀. Next, a four-element multiple-input multiple-output (MIMO) linear antenna array is presented to further verify the decoupling method and good isolation performance is also obtained, which demonstrates that the proposed designs are good candidates for 5G MIMO applications.