This paper presents a simple, low cost compact microstrip antenna, which works in triple frequency band. This compact microstrip antenna realized by changing the geometric shape, obtained by inserting a vertical slot. The simulation has been performed by simulation software GEMS version 7.71.01 and using Taconic TLY-5 dielectric substrate with relative permittivity 2.2 and height 1.588mm. The simulated return losses are obtained −21dB, −23.67dB and −9.859dB at 7.7GHz, 16.2GHz and 22GHz respectively. Therefore, this antenna can be applicable for C-band, Ku-band and K-band applications respectively.