A golf ball includes an inner core layer formed from a thermoplastic material. The inner core has a center hardness that is greater than the surface hardness to define a negative hardness gradient. An outer core layer is disposed about the inner core. The outer core has a surface hardness that is greater than the surface hardness of the inner core to define a positive hardness gradient. An inner cover layer and an outer core layer are formed over the outer core layer. The negative hardness gradient of the inner core is about −1 to −5 Shore C, the positive hardness gradient of the outer core layer is less than 25 Shore C, the surface hardness of the outer core layer is about 45 Shore D to about 70 Shore D, and the surface hardness of the inner core is about 20 Shore D to about 60 Shore D.