In this paper, Coaxial feed dual band circular Microstrip patch antenna (CMPA) for ISM (2.4–2.5GHz) and WLAN (5.150–5.350GHz) application is proposed. Dual frequency bands are obtained by inserting a circular slot in the circular radiator as well as bandwidth enhancement is obtained by modifying the ground plane. FR-4 substrate having dielectric constant of 4.4 and thickness of 1.6 mm is used to simulate CMPA and an overall size of CMPA is 40 × 40 × 1.6m3. The designed antenna simulated using CAD FEKO simulation software. The proposed antenna achieves S11 < −10dB. Maximum bandwidth observed is about 78MHz for ISM band and 190MHz for WLAN band.