A golf shoe with a sole assembly having a sidewall reinforcement structure is provided. The reinforcement structure may be formed from a carbon composite or other reinforcing material. The reinforcement structure is molded into the sole assembly for reinforcing softer midsole sidewalls, and for providing increased stability and maintaining forefoot flexibility. The structure is generally U-shaped with a medial and lateral wing and a bridge connecting the wings. The medial wing may be angled rearward to support the rearfoot, and the lateral wing may be angled forward to support the midfoot. Thus, the reinforcement structure may hold and support the medial and lateral sides of the golfer’s foot as they shift their weight while making a golf shot. At the same time, the shoe has good flexibility so the golfer is able to walk and play the course and engage in other golf activities comfortably.