An imaging lens assembly includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element and a fourth lens element. The positive first lens element has a convex object-side surface at a paraxial region. The negative second lens element has a concave image-side surface at a paraxial region, wherein the image-side surface thereof has a convex shape at a peripheral region, and the surfaces thereof are aspheric. The positive third lens element has a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region. The negative fourth lens element has a concave image-side surface at a paraxial region, wherein the image-side surface thereof has a convex shape at a peripheral region, and the surfaces thereof are aspheric. The imaging lens assembly has a total of four lens elements with refractive power.