A grip adjusting insert for a hole in a bowling ball. An outer sleeve is inserted in the hole in the bowling ball, an inner sleeve is movably mounted in the sleeve, and a finger-engaging member is affixed in the inner sleeve and conforms to a finger of a user. The outer sleeve has a pair of throughslots that are inverted T-shaped. The inner sleeve has a pair of pins that ride axially downwardly in the pair of throughslots in the outer sleeve, respectively, when the inner sleeve is inserted into the sleeve, and at which time, the inner sleeve is rotated relative to the outer sleeve so as to cause the pair of pins to move laterally in the pair of throughslots in the outer sleeve, respectively. The finger-engaging member is rubber poured into the inner sleeve, with a finger therein so as to conform thereto.