We investigate whether, why and when prosocial engagement has a causal effect on individual employment opportunities. To this end, a field experiment is conducted in which volunteering activities are randomly assigned to fictitious job applications sent to genuine vacancies. We find that volunteers get one third more interview invitations than non-volunteers. The volunteering premium is higher for females but invariant with respect to the number of engagements and the private versus public or nonprofit orientation of the job posting firm. As a result, our findings are consistent with the idea that prosocial workers sort themselves into non-commercial sectors.