A low-profile aperture-coupled microstrip patch antenna (MPA) under multiresonant modes for wide half-power beamwidth (HPBW), high gain and enhanced-bandwidth is proposed. Firstly, the radiation patterns of the MPA are studied to improve the radiation performance. It demonstrates that the HPBW of the lower TM10 mode could be progressively widened by properly selecting the dielectric constant of the substrate. Meanwhile, by etching a rectangular slot, the high sidelobe in E-plane of the upper TM30 mode could be obviously reduced, resulting in enhancing the normal gain. Secondly, the improved feeding network is introduced and studied. The results show that the impedance bandwidth of the antenna is successfully extended over dual operating bands. Finally, the proposed antenna is fabricated and tested. Experimental results show that the antenna has improved-bandwidths (|S11| < -10 dB) with two-minimum poles in the range of 1.42-1.45 GHz for the lower band and 3.95-4.13 GHz for the upper band, respectively, which is about two times wider than that of the traditional counterpart. Besides, the antenna maintains the small thickness of about 0.02 free-space wavelength. Particularly, the wide E-plane HPBW and broadside gain of the MPA are simultaneously enhanced to around 130° and 9.0 dBi at the lower and upper bands, respectively.