A golf putter grip accessory includes a protruding grip body and a clamping assembly. The grip body includes an inner surface designed to face a golf putter grip when the golf putter grip accessory is removably attached to a golf putter, and an outer surface that is ergonomically contoured to provide a gripping surface for an extended index finger of a user to assist a user in holding the golf putter straight. The clamping assembly is attached to the grip body and designed to releasably attach the golf putter grip accessory to the golf putter.