This letter proposes a wideband filtering differential phase shifter with enhanced harmonic suppression. Through the original transmission line model, the numerical relationship between the prescribed amplitude/phase response and the initial design parameters can be readily established. Then the simple transformation from the transmission line to its T-type lowpass network is utilized to suppress the harmonics efficiently with almost the same in-band phase shift response. For demonstration, a prototype is designed and fabricated, the proposed filtering phase shifter features enhanced harmonic suppression up to 3.5f0 and an enhanced suppression level of 33.5 dB.