Taxes represent a significant cost to the firm and shareholders, and it is generally expected that shareholders prefer tax aggressiveness. However, this argument ignores potential non-tax costs that can accompany tax aggressiveness, especially those arising from agency problems. Firms owned/run by founding family members are characterized by a unique agency conflict between dominant and small shareholders. Using multiple measures to capture tax aggressiveness and founding family presence, we find that family firms are less tax aggressive than their non-family counterparts, ceteris paribus. This result suggests that family owners are willing to forgo tax benefits in order to avoid the non-tax cost of a potential price discount, which can arise from minority shareholders' concern with family rent-seeking masked by tax avoidance activities (Desai and Dharmapala 2006). This inference is further strengthened by our finding that family firms without long-term institutional investors (as outside monitors) and family firms expecting to raise capital exhibit even lower tax aggressiveness. Our result is also consistent with family owners being more concerned with the potential penalty and reputation damage from an IRS audit than non-family firms. We obtain similar inferences when using a small sample of tax shelter cases.