Internet of things (IoT) is a complex network of physical objects capable of wirelessly communicating with each other. For implementing such an enormous network, the authors design a compact dual‐band antenna with simple structure. By folding the radiating element and resetting the ground plane, the whole size of the designed antenna is only 14 mm × 14 mm same as a thumbnail, which makes the designed antenna easy to fabricate. The fabricated antenna can operate (return loss S11<−10 dB) at two operating bands of 3.4–3.6 GHz for 5G and 5.725–5.825 GHz for 5.8G Wi‐Fi, which means it is able to connect the IoT nodes to the Internet through 5G and Wi‐Fi network. Simulation and measured results demonstrate that (i) folding the L‐shaped stub into U‐shaped can reduce the dimension of antenna, and resetting the ground plane structure to parallel to the feed‐line can achieve better impedance matching between the designed antenna and the sub‐miniature‐A (SMA) connector in both operating bands; (ii) the fabricated antenna is able to fully cover the operating bands of 5G at 3.4–3.6 GHz and Wi‐Fi at 5.725–5.825 GHz, and can achieve nearly omnidirectional radiation patterns over the two operating bands.