A tankless water heater carrier having a pair of load supporting brackets, a slot formed through each load supporting bracket, and a pair of rigidity rails extending longitudinally along each side of each load supporting brackets. The tankless water heater carrier has a pair of side brackets connected between the pair of load supporting brackets, a pair of sliding brackets moveably mounted onto each load supporting bracket, and a plurality of removable threaded rough in guides positioned in the alignment holes of each sliding bracket and through the slots of the load supporting brackets. The tankless water heater carrier includes fasteners usable to connect the side brackets to the load supporting brackets and to connect the sliding brackets to the load supporting brackets creating a theft resistant tankless water heater that is versatile for all sizes.