An imaging system lens assembly includes six lens elements which are, in order from an object side to an image side along an optical path: a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element. Each of the six lens elements has an object-side surface facing toward the object side and an image-side surface facing toward the image side. The first lens element has positive refractive power. The image-side surface of the fifth lens element is convex in a paraxial region thereof. The image-side surface of the sixth lens element is concave in a paraxial region thereof, and the image-side surface of the sixth lens element has at least one inflection point.