Porosity and pore space arrangement are essential for heat transfer and the reduction process of iron ore pellets in steelworks. Therefore, the pellet microstructural characterization becomes important for the quality control of the final product, steel, helping in the understanding of its behavior in the blast furnaces. Currently, the most used techniques for characterization are optical microscopy, which offers only two-dimensional results and thus does not represent exactly the reality; and mercury intrusion porosimetry that evaluates only pores connected to the surface, and uses mercury, which is highly harmful to human health. Moreover, they are techniques considered destructive as it is not possible to do other analyzes in the same samples, since they are destroyed. This work proposes to optimize a methodology of three-dimensional characterization of porosity in pellets using the technique of x-ray microtomography (microCT). This is a non - destructive technique that provides 3D information, but presents limitations related to the time of analysis and resolution. It was possible to characterize in 3D pellet samples provided by the Vale company, obtaining the porosity and the pore volume distribution. Open and closed porosity was also measured by a new developed methodology. Thus, the acquisition methodology was optimized, reaching a reduction of time for all the analyzes - it took 3 hours for the analysis of an entire ball. It was confirmed that the resolution had a great impact on the porosity characterization of iron ore pellets, evidenced by the great difference between the porosities measured at the different resolutions reached: 14.83 percent for 7.6 micrometers, 23.69 percent for 4 micrometers and 26.75 percent for 2 micrometers.