We demonstrate a technique for fabricating microstrip patch antennas using femtosecond laser patterning followed by ultraviolet beam and chemical treatment. Initially, we design the physical parameters of both single-slot and double-slot microstrip patch antennas and simulate them using high-frequency structure simulator for optimization. Simulation results exhibit a return loss of −26 dB at the resonant frequency of 22.9 gigahertz (GHz) for single-slot microstrip patch antenna and −18.3 dB at 24.03 GHz for double-slot microstrip patch antenna. The three-dimensional polar plot and far-field radiation pattern of the microstrip patch antennas confirm excellent directivity of the antennas. Furthermore, we investigate the return loss of the fabricated microstrip patch antennas. For single-slot microstrip patch antenna, experimental result shows a return loss of −21.25 dB at 22.7 GHz. In contrast, double-slot microstrip patch antenna shows a return loss of −27 dB at 24.1 GHz. In addition, we compare the performance of the double-slot microstrip patch antenna fabricated using femtosecond laser-assisted technique and photolithographic technique and find better performance in the femtosecond laser-fabricated microstrip antenna. The proposed femtosecond laser-based technique is simple and shows promises in precise fabrication of high-quality microstrip antennas.