A lens for an LED includes a top face, a bottom face, and a circumferential periphery interconnecting the top and bottom faces. The top face defines a recess therein. A concave wall defines a bottom of the recess. In cross section of the lens, the concave wall consists of two symmetrical curves extending outward and upwardly from a bottom tip of the recess to connect with the top face. Each curve is a part of a hyperbola. The cavity is for receiving an LED therein. The lens further forms a cone-shaped top wall enclosing a top of the cavity. Light emitted from the LED travels through the cone-shaped top wall to strike the concave wall and be reflected thereby to radiate sideward and downwardly. The sideward and downwardly reflected light then is reflected by a reflective coating on a substrate to illuminate upwardly.