In this paper, an alternative out-of-phase wideband filtering power divider (FPD) is proposed by using slotline resonators and microstrip-to-slotline structure. A unique wideband performance is attained by using the coupling between microstrip line and slotline resonator. The required reverse phase can be achieved by loading quarter wavelength output open lines. Meanwhile, nice port-to-port isolation can be attained by inserting a chip resistor at the junction of the circular slot and the slotline stub, which is located just underneath the T-shaped transmission line. To validate this design concept, one out of phase wide-band FPD prototype is designed and simulated, and simulation results show good wideband out-of-phase power division characteristics.