An imaging optical lens assembly includes seven lens elements, the seventh lens elements being, 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, a fifth lens element, a sixth lens element, and a seventh lens element. The first lens element with positive refractive power has an object-side surface being convex in a paraxial region thereof. The second lens element has negative refractive power. The seventh lens element has an image-side surface being concave in a paraxial region thereof and having a critical point in an off-axis region thereof. The image-side surface and an object-side surface of the seventh lens element are both aspheric.