A portable projector screen assembly includes a roller, two cylinders slidably connected to two ends of the roller respectively, a collapsible member connected to the roller, and a screen. The collapsible member includes a plurality of interconnected pieces. Two free ends of the collapsible member are fixed to free ends of the cylinders respectively. The screen includes a plurality of fixing portions, and the fixing portions are respectively connected to joints of each two pieces of the collapsible member.