This project quantifies, for the first time, the greenhouse gas (GHG) emissions co-benefits associated with water, waste and transportation usage in certified green commercial office buildings in California. The study compares the measured values of water, waste and transportation usage self-reported by a set of office buildings certified under the Leadership in Energy and Environmental Design rating system for Existing Building Operations and Maintenance (LEED-EBOM) to both baseline values of conventional California office buildings and predicted values based upon state standards for green buildings and GHG impact prediction methods. The green buildings in the LEED-EBOM dataset produced 50% less GHGs due to water consumption than baseline buildings, 48% less due to solid waste management, and 5% less due to transportation. If applied to the entire California office building stock, performance typical of the certified green buildings would save 0.703 MMTCO2e/yr from transportation, 0.084 MMTCO2e/yr from water, and 0.044 MMTCO2e/yr from waste, for a total potential savings of about 0.831 MMTCO2e/yr relative to conventional construction. In addition, buildings earning additional credits for specified performance thresholds for water and waste in the LEED-EBOM code attained performance levels even higher than required by the code provisions, suggesting that such code provisions in other contexts may help incentivize larger GHG emissions reductions than anticipated.