This paper examines the relationship between corporate ownership structure in Portugal and earnings management. The Portuguese governance structure is characterised by the dominance of the largest shareholder who typically exercises significant influences on management decisions directly or indirectly. Existing literature suggests that ownership structure decreases the incentive to manage earnings but also provides the opportunity and incentive to anipulate earnings. Therefore, the main purpose of this paper is to analyse whether a firm’s ownership structure (measured with three variables: managerial ownership, ownership concentration and institutional ownership) exacerbate or alleviate earnings management. Using a sample of 34 non-financial listed Portuguese firms for years from 2002 to 2007, we find that discretionary accruals as a proxy for earnings management is negatively related both to managerial ownership and to ownership concentration. The study’s results suggest that both managerial ownership and ownership concentration improve the quality of annual earnings by reducing the levels of earnings management.