In this paper, we present an extremely compact ultrawideband (UWB) monopole microstrip patch antenna for a wireless body area network (WBAN). The proposed antenna is fabricated on a flexible Rogers RT-5880 dielectric substrate of thickness 0.5 mm and has an overall size of 20×15×0.5 mm3. The proposed antenna achieves a wideband characteristic with the help of a modified ground plane with a monopole pair. The monopole antenna is fed through a microstrip line and has a good impedance matching over a frequency band of 3.2 to 15 GHz (and beyond), with an axial ratio below 3 dB and a high efficiency of 77–95%. This antenna is designed to cover almost the complete UWB range; bandwidth for antenna is 11.52 GHz (3.48-15 GHz). The antenna has a realized gain of 2.3–7.2 dBi throughout the frequency band and has been tested for conformality. Measured results are found to be in good correlation with the simulated results. The antenna has also been tested for specific absorption rate (SAR) values within the simulation to compare with Federal Communications Commission (FCC) limits and verify their suitability for the Internet of Things- (IoT-) based wearable body area network.