An optical imaging lens system includes five lens elements which are, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, a fourth lens element and a fifth lens element. The first lens element has positive refractive power. The second lens element has negative refractive power. The third lens element has positive refractive power. The fourth lens element has negative refractive power. The fifth lens element with negative refractive power has an object-side surface being concave in a paraxial region thereof.