Abstract: A machine for packaging a mattress in a sheet, comprising horizontal supporting and receiving mattress surfaces, guides for guiding the sheet on a vertical plane, so that by moving the mattress in the advancement direction from the supporting surface toward the receiving surface the sheet is arranged over and under the mattress, a device for joining and cutting the sheet upstream of the mattress and for forming a bag which wraps around the mattress, sheet unwinding assemblies comprising two rollers movable along the receiving surface with a return stroke, the rollers being articulated to rotate between alignment and parallel positions in which they are perpendicular or parallel to the advancement direction and to the sides of the mattress, and actuators for actuating the rollers.