While stewardship theory is often used to explain family business outcomes, no prior empirical study has used a validated measure of stewardship. We, therefore, surveyed 846 managers and subordinates from 221 family and nonfamily firms in the United States and Australia to develop a reliable and valid Stewardship Climate Scale. We found family firms have a stronger stewardship climate and the relationship between stewardship climate and performance is mediated by innovativeness, and the effects of stewardship are stronger in family firms, confirming the value of stewardship theory, and our scale, when explaining family business outcomes.