There is remarkable cooperative organization scarcity in the United States. Particularly in the credit union and worker cooperative sectors, this scarcity is not satisfactorily explained by neo-classical economic models that assume competitive conditions and profit-maximizing organizations. This paper supplements the conventional economic understandings of credit union and worker cooperative scarcity with an institutional analysis. Mechanisms of coercive, mimetic, and normative institutional isomorphism developed in DiMaggio and Powell’s theory of organizational isomorphism are applied to provide greater understanding of credit union and worker cooperative scarcity in the US. It appears that these forces of isomorphism work in conjunction with one another, as well as with competitive forces of isomorphism, to cyclically reproduce the scarcity of credit unions and worker cooperatives which prevails in the US.