Development of a simple process for separating cellulose and polyester from their mixed fabrics is indispensable for the recycling of waste mixed fabrics. The authors have developed an efficient two-step procedure that consists of an acid treatment and successive mechanical treatment of the mixed fabrics, or more specifically a 1-min static acid treatment of the mixed fabrics with 95 °C aqueous 10 N H2SO4 and successive mechanical beating in room-temperature water. The procedure was also found to be effective for the separation of regenerated cellulosic fabrics from their mixed fabrics with polyester. Cellulose was efficiently removed from polyester fabrics as a powder, with high recovery of both cellulose powder and polyester cloth.