Organic coverlays are required to protect microstrip circuits in most applications. The presence of coverlay can potentially influence the performance of microstrip antennas. This paper describes the qualification of polyimide based coverlays for microstrip antennas both in 900 MHz and 2.50 GHz frequency bands. An Inverted F-shaped antenna fabricated on FR-4 dielectric is used as the test vehicle and two different coverlay materials are tested with respect to key parameters like resonant frequency, S11 bandwidth, antenna gain, frequency detuning, and radiation pattern. The data presented in this paper clearly indicates polyimide materials are well suited to cover microstrip antenna circuits with minimal impact on performance.