Synthesis method for a novel dual‐band Wilkinson power divider (DBWPD) is presented in this study. The proposed DBWPD is constructed using a novel dual‐band impedance transformer (DBIT). The DBIT is made up of a kernel circuit unit cell with uniform transmission lines attached to its two ends. A non‐linear system of equations ruling the DBIT performance is first built up and then successfully solved with numerical method. Design charts are provided for determining the feasible DBIT theoretical parameters. With the DBIT theoretical solutions, a microstrip DBWPD operative at 2.4/5.2 GHz is practically implemented, of which layout parameters are effectively resolved in a sequential three‐step optimisation design process, and its compact size as well as good dual‐band operation performance has been demonstrated by fabrication and experimental tests, confirming the proposed synthesis method.