Abstract: A sink stopper assembly includes cup and basket strainers. The cup strainer includes a bottom wall having a positioning hole, and a shoulder portion forming a seat member. The basket strainer is disposed in the cup strainer, and includes a receiving space, a handle extending upwardly from a base wall, a sealing ring to be seated against the seat member, and a retaining stem extending downwardly from the base wall to penetrate the positioning hole. The retaining stem includes a bent metal plate which has two opposite elastic arms, at least one upper protrusion, at least one lower protrusion, and a recess defined between the upper and lower protrusions.