This paper extends research on nonprofit advocacy by exploring the relationship between competition, nonprofit mission, and policy advocacy. Previous research indicates that charitable nonprofits serving specialized populations, such as immigrants or veterans, often engage in policy advocacy. This could benefit marginalized populations whose interests are articulated by nonprofit organizations. However, population ecology theory in organizational sociology predicts that generalist organizations will outperform specialists in uncertain environments. At the very times when nonprofits serving specialized constituencies should focus on advocacy the most – for example to protect funding in competitive policy environments – they may be least able to do so. Drawing on survey data from charitable nonprofits in Boston, Massachusetts, we find that competition and specialization have direct positive effects on nonprofit engagement in advocacy and the use of formal and grassroots tactics. However, the effect of competition is weakened by nonprofit specialization. Nonprofit specialists that report higher competition for resources are less likely to participate in policy advocacy and use fewer formal and grassroots tactics. Specialists that report higher service delivery competition use fewer formal advocacy tactics. These findings suggest that we should be cautious in looking to the nonprofit sector, particularly organizations serving specialized populations, to provide constituent representation through policy advocacy in competitive environments.