Objective: Resin infiltration is an innovative microinvasive measure, whereby hard tissues are preserved, that has been used to treat medium stages of caries. The aim of this study is to evaluate with Confocal laser scanning microscopy the indirect staining technique of resin infiltration in teeth with different degrees of fluorosis. Methods: Twenty-four fluorosed human molars and premolars were infiltrated and light cured. Specimens were prepared and lesions, as well as penetration depth were analyzed using dual fluorescence method in confocal laser microscopy. Results: Percentage penetration, was significantly higher in teeth with mild and very mild fluorotic lesions, unlike moderate and control group which was significantly lower (p < 0.05, Bonferroni test). However, there are no statistically significant differences between control and moderate groups neither between very mild and mild groups (p &gt; 0.05, Bonferroni test). Conclusion: It can be concluded that resin penetration in mild and very mild fluorotic lesions is higher than in moderate lesions.