A new gain-enhanced patch antenna with loading of shorting pins is proposed in this paper. Four metallic pins are symmetrically placed in the two diagonals of a square patch resonator to electrically short the patch and ground plane. These shorting pins tremendously perturb the field distribution beneath the patch due to their shunt inductive effect. As these four pins are moved outward along the two orthogonal diagonals away from the center, their influence on the field distribution over the patch is strengthened to gradually raise its dominant mode, i.e., TM010 mode, resonant frequency as the pin-to-pin spacing is enlarged. At a fixed resonant frequency, the overall area of this proposed patch antenna with four pins results to be increased. As such, its radiation directivity or gain gets to be enhanced due to the enlarged antenna area. After extensive analysis is executed, two square patch antennas with and without loaded pins are designed and fabricated. The simulated and measured results agree with each other, and they have evidently demonstrated that the radiation directivity can be enhanced up to 11.0 dBi, or about 2.9 dB increment, by virtue of the proposed approach.