Background: The era of flexible antennas started long ago because they are cost-effective while offering several advantages, such as good flexibility, stretchability, and compactness. Although several synthetic and natural polymers with good flexibility are available, the first flexible antenna is designed with polyimide materials (polymers), often known as engineering plastics. Objective: To fabricate a compact antenna with a higher gain than other existing ones and the bending loss of the proposed antenna is lower than other existing ones, this study proposes an ideal antenna. Methods: A polyimide (PI)-based flexible antenna with a defected ground structure is proposed for telemedicine and wireless applications, and we implement this antenna using microstrip feeding. The proposed antenna consists of a polyimide substrate with a thickness of 0.1 mm, a relative permittivity of 3.15, a loss factor of 0.0013, and a compact overall size of 25 x 32 x 0.1 mm3. Results: The proposed antenna operates on three frequencies, including 2.4 GHz (ISM or telemedicine application), 5.5 GHz (WiMAX band), and 7.5 GHz (wireless radio band). The proposed antenna produces impedance bandwidths of 10.16%, 14.54%, and 5.33% at frequencies of 2.4 GHz, 5.5 GHz, and 7.5 GHz, with gains of 4.9 dB, 5.1 dB, and 5 dB. Conclusion: The proposed antenna is simulated using Ansys High-Frequency Structure Simulator (HFSS) software. A good agreement is found between the measured and simulated results.