This paper presents the miniaturization of a three-port power divider for microwave frequency. The size reduction is achieved by the use of a quarter-wave-like transformer (QWLT) implemented by a properly designed conjugately characteristic-impedance transmission line (CCITL). The QWLT has a significantly shorter physical length than the conventional quarter-wave transformer (QWT). A novel condition for the isolation impedance has been derived and presented in this paper. The size reduction of the power divider can consequently reduce the whole dimension of the circuit composing the divider with insignificant performance degradation, and thus decreasing the manufacturing cost.