An optical imaging system includes ten lens elements which are, in order from an object side to an image side along an optical path: a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element, a seventh lens element, an eighth lens element, a ninth lens element and a tenth lens element. Each of the ten lens elements has an object-side surface facing toward the object side and an image-side surface facing toward the image side. The second lens element has negative refractive power. The tenth lens element has negative refractive power, and at least one of the object-side surface and the image-side surface of the tenth lens element has at least one inflection point.