Abstract: A ball joint assembly for a vehicle includes a mounting part including an inner circumference part forming a hole in a vertical direction; a ball stud including a ball and a stud extending from the ball; a bearing coupled to surround the ball and disposed in the hole; and an insert molding part for filling the space of the hole formed between the inner circumference part and the outer surface of the bearing. The inner circumference part includes at least one upper protruding part protruding from an upper area thereof in a direction toward a central axis of the hole and at least one lower protruding part protruding from a lower area thereof in a direction toward the central axis.