An imaging lens assembly includes, in order from an object side to an image side, a first lens element (100), a second lens element (120), a third lens element (130), and a fourth lens element (140). The first lens element (110) with positive refractive power has an object-side surface (111) being convex. The second lens element (120) with negative refractive power has an object-side surface (121) being concave. The third lens element (130) with positive refractive power has an object-side surface (131) and an image-side surface (132) being both aspheric. The fourth lens element (140) with refractive power has an object-side surface (141) and an image-side surface (142) being aspheric.