A device and method for strengthening a natural fingernail includes a nail reinforcing device made of a pliable and conformable material having a thickness that is less than the thickness of a natural fingernail. The nail reinforcing device can be preformed and shaped to correspond to the shape of a natural fingernail or can be shaped to correspond to the general shape of the natural fingernail to which it is attached or adhered. A method for strengthening a natural fingernail of the present invention comprises applying an adhesive to at least a portion of the bottom (underneath) surface of the free end of the natural fingernail, to at least a portion of the top surface of the natural fingernail, or to at least a portion of the upper surface of the nail reinforcing device. The body of the nail reinforcing device is then positioned and maintained under the natural fingernail so as to provide contact between the upper surface of the nail reinforcing device and the bottom surface of the natural fingernail. The sides of the nail reinforcing device are then folded so as to place the upper surface of the nail reinforcing device in contact with the top surface of the natural fingernail. The sides of the nail reinforcing device may be shaped to form decorative patterns on the top surface of the natural fingernail. The method and device can also be used for reattaching a broken fingernail by attaching or adhering the nail reinforcing device to the bottom surface of the detached and remaining portions of the broken fingernail. The method and device can also be used to repair a damaged fingernail. Once the nail reinforcing device has been attached or adhered to the natural fingernail, a filler material is applied to a portion of the nail reinforcing device underlying a damaged portion of the fingernail.