Abstract Planning for floating offshore wind development along the U.S. west coast has prompted questions about how this new ocean use may impact marine ecosystems. Previous research suggests that offshore wind farms will alter wind dynamics and upwelling in this region, but impacts on biogeochemistry have not yet been explored. Here, we employ a regional atmosphere‐ocean‐biogoechemistry modeling framework to evaluate the ocean response to simulated wind energy development off Oregon and California. The largest impacts occur during peak upwelling season off central California. Wind stress curl changes at the edges of the wind wake lead to an onshore/offshore dipole of decreased/increased upwelling and associated nitrate supply. Coherent increases and decreases to phytoplankton and zooplankton biomasses occur on larger spatial scales than the wind wake, resulting from circulation changes that alter local nitrate availability. Regional biomass changes are up ±20%, small relative to natural interannual variability, while spatially integrated changes are <1%.