A method for washing platelets includes introducing anticoagulant into a platelet product container, drawing re-anticoagulated platelet product from the platelet product container, and introducing it into a centrifuge bowl. The centrifuge bowl separates the platelets from the supernatant in which they are suspended. The method then washes the platelets by introducing wash solution into the centrifuge bowl. As the wash solution is introduced into the bowl, it displaces the supernatant from the bowl and into a waste container. The method then introduces platelet additive solution into the centrifuge bowl, which displaces the wash solution from the centrifuge bowl and into the waste container and further wash the platelets. The method then repeatedly accelerates and decelerates the centrifuge bowl to resuspend the platelets in the platelet additive solution.