Disclosure: The author is an academic partner at State Street Associates conducting research on ESG issues and sits on the advisory board of investment organizations that use ESG data. Editor's Note: Submitted 29 Sep 2019 accepted 23 Jan 2020 by Stephen J. Brown. Combining environmental, social, and governance (ESG) data with "big data" measuring public sentiment about corporate sustainability performance, I found that the valuation premium for strong sustainability performance increases as a function of positive momentum in public sentiment. An ESG factor long (short) on companies with superior (inferior) sustainability performance and negative (positive) ESG sentiment momentum delivered significant positive alpha. In contrast, the high-sentiment ESG factor delivered insignificant alpha and was negatively correlated with the value factor. The evidence suggests that public sentiment influences investor views about the value of sustainability activities and that big ESG data can be useful in identifying "value" ESG stocks.