A ladder assembly includes a ladder, two wheel carriers mounted on the ladder movably and rotatably, two wheels each rotatably mounted on a respective one of the wheel carriers, two fastening members each extended through a respective one of the wheel carriers and each secured on the ladder to attach the respective wheel carrier to the ladder, and a support rack pivotally mounted on the ladder. Thus, when the support rack and the wheels are expanded outward from the ladder, the ladder assembly can function as a carrier, and when the support rack and the wheels are folded onto the ladder, the ladder assembly can function as a ladder so that the ladder assembly both functions as a ladder and a carrier, thereby enhancing the versatility of the ladder assembly.