This paper examines the impact of ownership on product and international diversification. While ownership concentration has received considerable attention from agency theorists we argue that a more nuanced analysis is necessary. We consider how the identity of owners moderates the impact of ownership concentration on diversification strategies. We develop a framework that explains how the combination of different motivations, resources and capabilities associated with different types of owners results in significantly variable relationships between ownership concentration and both product and international diversification. From a theoretical perspective this suggests a social contextualization and extension of the agency theoretic approach that characterizes the field. Based on a study of 222 European firms between 1994 and 2007 we show that family ownership concentration has a positive impact on product and a negative impact on international diversification while the impact of institutional and state ownership concentration is negative on product diversification and positive on international diversification compared with family ownership. This is the first study to provide a comprehensive framework explaining how ownership concentration and identity interact and affect both international and product diversification.