The increase in researches related to nanomaterials has provided innovation and enhancement of the properties of innumerous materials. Among the materials frequently studied, magnesium oxide can be cited because of its many industrial applications, mainly in the chemical and electronics sectors. Magnesium oxide nanoparticles, as well as other nanomaterials, can be produced by several routes of synthesis, and the characteristics of the route chosen may change the microstructure and properties of the nanoparticles. However, despite the general consensus that the synthesis variables affect the characteristics and properties of the nanoparticles, much still needs to be studied. Among these variables, the reactive environment is one of the factors that influence considerably and about which there are still few studies. In this work, it was evaluated, using the sol-gel synthesis method, how the modification of the solvent, water or ethyl alcohol, affects the morphology and purity of the magnesium oxide nanoparticles, as well as the yield of the synthesis reactions. The nanoparticles were characterized by XRD, surface area analysis via BET, FEG-MEV and EDS. The results indicated that the nanoparticles obtained by route using ethyl alcohol as solvent have a larger crystallite and particle size, besides the synthesis reactions have a higher yield. In addition, by the analysis of surface area and pore volume, they present a lower surface area and lower pore volume, in relation to the route that uses water as solvent. Thus, it was possible to conclude that altering the solvent of the reaction, even if all other synthesis conditions are maintained, significant modifications are observed in the morphology of the magnesium oxide nanoparticles and also in the reaction yield.