In this article, a conformal antenna with ultrawideband performance is presented for wireless endoscopy applications, operating in industrial scientific, and medical (ISM, 433.1‐434.8 MHz) band. Rigid materials with high dielectric constants are typically used as substrates for implantable inverted‐F antennas (IFAs), but they are not suitable for conformal configurations. In contrast to this, the proposed antenna adopts flexible polyimide as its substrate. The original IFA is designed with a fundamental resonance in the lower band. By embedding an open‐slot between the short point and the feeding point, an additional resonance is excited, simultaneously moving toward the fundamental resonance, thereby achieving a simulation bandwidth of 100%. Finally, the proposed antenna is measured in pork.