The purpose of this article is to propose a novel design method for miniaturized tri-band Wilkinson power dividers with independently controllable center frequencies and a simple structure. Different from the traditional circuit of tri-band power dividers using three-section transmission-line transformers, this proposed structure consists of three-section coupled lines and three isolation resistors. Due to flexible even- and odd-mode parameters and inherent small size features of parallel coupled lines, this compact divider not only provides arbitrary tri-band operation but also increases the degrees of freedom in determining isolation performances. Furthermore, the simplified design equations for electrical parameters are obtained, and several ideal examples are demonstrated for initial theoretical verifications. As a remarkable example, a compact microstrip power divider operating at three industrial, scientific, and medical bands, namely, (0.92, 2.45, and 5.8 GHz), is designed, fabricated, and measured. There are good return loss (lower than −15.9 dB), small insertion loss (better than −3.8 dB), and excellent isolation (larger than 23.18 dB) performances at these desired triple bands in both the calculated and measured results.