An imaging lens assembly includes a plurality of optical elements, an optical axis passing through the optical elements is defined, and the optical elements include at least one mixing optical element. The mixing optical element includes a glass effective optical portion and a plastic outer peripheral portion. The optical axis passes through the glass effective optical portion. The plastic outer peripheral portion surrounds and physically contacts the glass effective optical portion, and forms an aperture hole. The plastic outer peripheral portion has at least three recess structures arranged and disposed along a circumference direction around the optical axis. The recess structures extend from one of the object side and the image side of the imaging lens assembly to the other thereof along a direction parallel to the optical axis. Each of the recess structures includes an outer surface, an inner surface and two side surfaces.