This letter presents a bandwidth-enhanced single-layer differential-fed microstrip patch antenna (MPA) under the operation of dual radiative TM ₃₀ and TM ₅₀ modes. A pair of long slots is symmetrically etched on specific positions of the upper microstrip patch, where the electric field of TM ₃₀ mode is at the peak point, while simultaneously the electric field of TM ₅₀ mode is at the null point. Thus, the capacitive effect of the installed slots effectively reallocates the TM ₅₀ mode to a much lower frequency region in close proximity to that the of less-influenced TM ₃₀ mode one, resulting in a wide operating bandwidth with dual-resonant radiation. Due to the same odd-order field distribution, the dual radiative modes produce the same maximum radiation in the broadside direction. Compared with other multimode patch antennas, the proposed one can be simply implemented in a single-layer substrate with the height of only 0.8 mm (0.0146 free-space wavelength at 5.5 GHz). An antenna prototype is designed, implemented, and measured. Tested results verify that the proposed antenna owns an enhanced operating -10 dB bandwidth of 6.1% (5.4-5.74 GHz) and a maximum realized gain of 10.7 dBi, demonstrating the advanced performance of the proposed dual-mode MPA.