Today export diversification has become one of the most important economic objectives of development strategies in the developing countries. For various reasons, such as preventing instability in export prices of primary products in global markets, reducing fluctuations in exchanges of them compared with industrial goods, producing dynamic benefits resulted from exporting various goods and increasing productivity of production factors may increase the rate of economic growth. The main purpose of this study is to investigate the role of export diversification in the economic growth of selected developing countries over the period of 2000-2010. Accordingly, the relationship among GDP, physical capital stock, labor force, and export diversification index was studied using the generalized method of moments (GMM). The results showed that reducing export specialization and increasing export diversification have significantly positive effect on the rate of economic growth of these countries.