A golf ball has a cover and a core surrounded by the cover. The core has an inner core and an outer core. The inner core is formed from a first composition and has a generally spherical shape and a spherical surface. The inner core has one or more blind holes that each extend from an opening at the spherical surface to a depth within the inner core. The outer core is formed from a second composition, different from the first composition. The outer core has a first portion that surrounds the inner core and a second portion that extends into each blind hole and thereby fills each blind hole of the one or more blind holes.