There are two dominant points of view in the field of Strategic Management to explain the firm performance: the Industrial Organization view, which highlights the role of the industrial environment, and the Resource Based View, which emphasizes the importance of the idiosyncratic characteristics of firms, both extensively studied. However, the association between the firm performance and the competitiveness of nations in terms of their institutional, cultural, political and economical environment is a field of knowledge still insufficiently explored. This study shows that firm performance depends not only on the industries to which they belong or to their individual characteristics, but also to the wider environment of the countries where they operate. From the Annual Competitiveness Reports of the World Economic Forum and the financial performance indicators obtained from the database of MSCI Inc., the hypothesis made relating the wider environment of the countries to the performance of their firms were tested. Evidences of the relationship between the nation´s competitiveness indicators and the sustainable performance of their firms were found. The study pioneered the approach relating the concept of competitive advantage of nations, through its indicators of competitiveness, to the competitive advantage of companies, through their performance; empirically tested the model of Michael Porter´s Competitive Diamond; highlighted three variables, usually neglected in the line of research of the sources of firm performance: Buyers Sophistication, GDP and Government Purchases; and created a new indicator of performance that also reflects its sustainability, which relates to the line of research on the persistence of abnormal returns.