A rethermalization system for rethermalizing refrigerated foods in an institutional food service setting is disclosed. A rethermalization cart is provided with a plurality of trays for supporting food items to be served. The trays are supported on heater shelves including heating elements located under the portions of the trays corresponding to locations of food items to be heated. A loaded cart is placed in a refrigerator and is attached to a power supply and controller. A serving time is programmed into the system and the controller provides power to the cart a predetermined interval before the desired serving time. Heater microcontrollers are associated with the heater shelves and control power to the heating element on the shelves in accordance with at least one rethermalization program.