Scientists, industry, and policy-makers have turned increasing attention toward the ocean as a source of climate change mitigation solutions. Efforts to develop ocean-based climate interventions (OBCIs) to remove and sequester carbon dioxide (CO2), manage solar radiation, or produce renewable energy have accelerated. Questions have been raised about OBCI costs, governance, impacts, and effectiveness at scale, but limited attention has been given to ocean biogeochemistry and ecosystems (1) and particularly to impacts on deepsea ecosystems (>200-m water depth), an ocean region that is understudied but fundamental for Earth’s healthy function. The deep sea, with low energy supply; typically cold, stable conditions; and a low density of organisms with reduced metabolism, requires specific attention. Here we discuss OBCIs that could affect deep-ocean ecosystems and their services, identify governance challenges, and highlight the need for an integrated research framework to help centralize consideration of deep-sea impacts in mitigation planning.