This paper presents the design of a passive RF matching network that can be tuned electronically to match a variable load impedance to a fixed source in the 2.4 GHz Industrial, Scientific and Medical (ISM) band. In principle, the design aims at maximum power transfer between the source and the load at any given frequency within the specified range. Theoretical analysis and simulation results have been presented to provide insight into the design of the pi-network circuit. An impedance tuner based on this theory was fabricated on a two-layered FR4 PCB. The fabricated tuner was tested for load impedances up to voltage standing wave ratio (VSWR) ≤ 6, wherein a maximum insertion loss of 4.1 dB was obtained at 2.45 GHz. A maximum insertion loss of 1.7 dB was observed for impedances up to VSWR ≤ 2.4. © 2018 IEEE.