An imaging lens assembly has an optical axis and includes a plastic barrel, a lens set and a retaining element. The plastic barrel includes a first channel and a second channel. The lens set is disposed in the plastic barrel and includes at least one adjustable lens element, wherein an outer diameter surface of the adjustable lens element includes a plurality of axial rotation structures, each of the axial rotation structures is in a protruding strip shape, and at least one of the axial rotation structures is disposed correspondingly to the second channel of the plastic barrel and exposed. The retaining element is disposed in the plastic barrel and includes an anti-releasing structure, which is disposed correspondingly to the first channel of the plastic barrel to avoid the lens set being released from the plastic barrel.