In this paper, we present a novel dual-band out-of- phase power divider with high power-handling capability. The proposed device consists of five ports including one input port, two output ports, and two extra ones, which are connected by the external isolation resistors. To obtain the out-of-phase feature between the two output ports, double-sided parallel-strip lines are employed, and a conductor plane is inserted in the middle of the substrate as a common ground. A set of closed-form design equations is developed for analysis of the novel design structure by using the rigorous even- and odd-mode analysis method. The analysis shows that the proposed power divider can operate at two frequencies of f1 and mf1 with a wide frequency ratio range at 1.62 <; m <; 3. Furthermore, the power operation analysis also illustrates that the new circuit is superior in high power-handling capability over the conventional dividers with internal isolation resistors. For verification, an example power divider with frequency ratios of 2.4:1 is implemented. Simulation and experimental results agree well, validating the proposed design methodology.