According to the Brazilian External Association of Commerce, iron ore represented 12,8 percent of total export revenue in 2012, being the first product, at value, on the Brazilian export market share. In this context, Carajás Complex, located at south east of Pará State in operation since 1985, express itself from being the biggest reserve in the country and for having the highest iron ore content of the world. The target of this work is to evaluate the Carajás expansion project, known as S11D project, through Real Option Theory, considering the value of management flexibility existing in this project and potential market uncertainties in which obtain a valuation more efficient from an asset so representative to the country. The results indicate that the expansion option raises the project value from 77 billion dollars to 99 billion dollars, resulting the option value of 22 billion dollars.