Governance of corporate sustainability conduct presents a particularly burdensome challenge because it relies on voluntary codes of conduct, minus regulatory mandates. Two major codes are examined and found to be seriously deficient in terms of institutional legitimacy. To deal with this issue, this chapter proposes the use of sustainability science at the corporate level to provide usable knowledge for the governance of corporate sustainability conduct. The proposal, built around five key questions, is then illustrated with two descriptive cases that examine water usage by two large multinational corporations in India and the United States.