An energy harvesting antenna array for wireless sensor applications is presented in this paper. The microstrip line feeding network excites four slots to achieve wireless local-areanetwork (WLAN) 2.4/5.2/5.8 (2.4–2.484/5.15–5.325/5.725–5.825 GHz) bands. The design is printed on a flame retardant 4 (FR4) substrate with thickness of 1.6 mm, permittivity of 4.4, and loss tangent of 0.0245. The overall size of the antenna array is only 60 × 60 × 1.6 mm3 and, with dual-ports, consists of two antenna arrays; port 1 is designed for a WLAN 2.4 GHz band and port 2 is designed for a WLAN 5.2/5.8 GHz band. The feeding network (electric length = λg/4) was used to connect the array network and antenna, and for the purpose of in phase excitation, we used microstrip lines (electric length = λg/2) to adjust the phase difference of these two antenna elements to 180°. Finally, 8 mm above the antenna array, we placed a metal reflector the same size as the antenna to adjust the radiation patterns to the −y direction and to enhance the radiation directivity and gains.