Turbulent mixing from breaking oceanic internal waves drives a vertical transport of water, heat and other climatically important tracers in the ocean, thereby playing an important role in shaping the circulation and distributions of heat and carbon within the climate system. However, linking internal wave-driven mixing to its impacts on climate poses a formidable challenge, since it requires understanding of the complex life cycle of internal waves — including generation, propagation and breaking into turbulence — and knowledge of the spatio-temporal variability of these processes in the diverse, rapidly evolving oceanic environment. In this Review, we trace the energy pathways from tides, winds and geostrophic currents to internal wave mixing, connecting this mixing with the global climate system. Additionally, we discuss avenues for future work, including understanding energy transfer processes within the internal wave field, how internal waves can be modified by background currents and how internal wave mixing is integrated within the global climate system.