Air pollution and air quality assessment is a serious problem for a big cities, considering the increasing of air contamination. In this work, an air quality assessment on three monitoring points located in three different districts from Lima city, Peru, was conducted. The method used in this study was the grey clustering method, which is based on the grey system theory. This method has advantages, as it considers the uncertainty into its analysis, and air quality assessment is a topic with high level of uncertainty. The results revealed that the three monitoring points presented a good air quality according to Peruvian law. This is due to the fact that the districts on which are locates the monitoring points are new relatively; in addition, the wind from ocean helps to disperse the air pollution. The results of this study could to help to local and central authorities to make the best decision on air quality assessment. In addition, government from Peru could use the method applied in this word as an alternative to assess the air quality from other points of country.