We develop theory and a tightly-linked field experiment to explore the supply side implications of corporate social responsibility (CSR). Our natural field experiment, in which we created our own firm and hired actual workers, generates a rich data set on worker behavior and responses to both pecuniary and CSR incentives. Making use of a novel identification framework, we use these data to estimate a structural principal-agent model. This approach permits us to compare and contrast treatment and selection effects of both CSR and financial incentives. Using data from more than 110 job seekers, we find strong evidence that when a firm advertises work as socially-oriented, it attracts employees who are more productive, produce higher quality work, and have more highly valued leisure time. In terms of enhancing the labor pool, for example, CSR increases the number of applicants by 25 percent, an impact comparable to the effect of a 36 percent increase in wages. We also find an economically important complementarity between CSR and wage offers, highlighting the import of using both to hire and motivate workers. Beyond lending insights into the supply side of CSR, our research design serves as a framework for causal inference on other forms of non-pecuniary incentives and amenities in the workplace, or any other domain more generally.