Air-sea sensible and latent heat fluxes are fundamental to tropical cyclone (TC) energetics, but the impacts of seastate-dependent sea spray heat fluxes on TC structure and intensity are poorly understood. We explore these impacts herein by implementing a recently-developed parameterization for air-sea heat fluxes with seastate-dependent spray physics into a fully coupled atmosphere-wave-ocean model, the Unified Wave INterface–Coupled Model. We conduct model experiments with and without spray for four TCs covering wide ranges of intensity and structure. The effects of spray on model TCs in the open ocean can be summarized in three stages. 1) Spray evaporative cooling dominates in boundary layers (BLs) of tropical storms and weak hurricanes (i.e., with 10-m windspeeds ≲ 30–40 m s-1 and relatively small waves), which hinders intensification. 2) Further TC intensification increases spray generation, producing positive spray sensible heat fluxes (i.e., warming) under the eyewall. This warming is favorable for intensification, but inefficiency caused by cooler BL inflow continues to inhibit eyewall deep convection, and spray continues to oppose intensification overall. 3) Further increase of spray production from continued TC intensification (i.e., past Category 3) ultimately allows spray to promote intensification by warming the BL and enhancing eyewall deep convection. Spray’s tendency to oppose intensification of weak TCs is consistent with the relatively rare occurrence of major hurricanes. However, if a TC intensifies beyond stage 2, spray can support rapid intensification. We also find that enhanced spray generation by wave dissipation in the coastal zone may strengthen landfalling TCs.