This paper presents a planar dual-band slim microstrip patch antennas. The antenna comprises four sections: patch and shorting, centered, and offset pins with the overall size of 30 × 50 mm ² . It is shown that the centered and offset pins help to improve antenna matching while providing efficient radiation performance. With the aid of shorting pins, lower band operation at 1900 MHz is achieved. Moreover, the higher frequency band is expanded from 3480 to 3570 MHz. Simulations show that at the lower band frequencies, the antenna gain and efficiency are 1.0 dBi and 28%, respectively. On the other hand, at the upper frequency band, the antenna maximum gain is 2.4 dBi, and the efficiency of at least 25% is observed. The numerical simulation shows that the number of resonant frequencies is directly related to the patch width. In order to validate the simulation results, a prototype of the proposed antenna is fabricated and measured. Good agreement has been achieved between the simulation and measurement results.