An image forming system includes an image forming apparatus and a sheet laminator. The image forming apparatus forms an image on a sheet being conveyed as an inner sheet. The sheet laminator performs a sheet laminating operation on a two-ply sheet in which the sheet conveyed from the image forming apparatus is inserted between two sheets of the two-ply sheet. The sheet laminator includes a heater and circuitry. The heater heats the two-ply sheet during the sheet laminating operation. The circuitry is to execute a control mode when a specific abnormal event occurs among a plurality of abnormal events that occurs in the image forming apparatus, where the control mode maintains heating by the heater of the sheet laminator for a predetermined time and interrupt the heating by the heater when an abnormal event other than the specific abnormal event occurs.