An image sensor package includes a substrate, a sensor chip, a frame, a lens element and at least a pair of guide pins. The sensor chip is mounted on the substrate, and has two opposite sides and a sensing region, which has a sensing region central axis. The frame is mounted on the substrate, and has an aperture and an inner space with the sensor chip disposed therein. The lens element is disposed inside the aperture and has a lens central axis. The guide pins locate oppositely inside the inner space of the frame with an interval between the tips of the guide pins substantially identical to the distance between the opposite sides of the sensor chip, wherein the central line of the interval between the tips of the guide pins defines a positioning line, which substantially coincides with the lens central axis; wherein the tip of each guide pin is aligned with one of the opposite sides of the sensor chip such that the positioning line is substantially coincided with the sensing region central axis.