A heat shrink tunnel with width adjustment includes a pair of opposing side wall assemblies, each assembly including an outer wall and an inner perforated wall defining a plenum therebetween. The opposing side walls define a product path therebetween having a longitudinal axis. The side wall assemblies are movable toward and away from the axis. A heater/blower assembly is disposed in each of the opposing side walls, each having an outlet directed into the product path and drawing air from the product path, through its respective plenum. A top wall extends between the pair of opposing side wall assemblies and has an adjustable width to accommodate movement of the side wall assemblies.