A dual-wideband differential filter with intrinsic common-mode suppression is presented. The filter is composed of three coupled strip-loaded slotline resonators and strip- loaded coupled slotlines with enhanced coupling strength. Two resonant modes of each resonator are utilized to design the desired dual-wide passbands, whereas the coupling coefficients in two passbands can be independently controlled to achieve dual-band frequency selectivity. The theory and design have been verified experimentally.