Aim: This study aimed to determine in vitro the effect of Tooth Mousse [a commercial paste based on Casein phosphopeptides-amorphous calcium phosphate (CPP-ACP) complex] on the remineralization of demineralized enamel surfaces. Materials and methods: Thirty human enamel specimens were divided into two equal groups (n=15).Group A was topically treated with CPP-ACP paste (Tooth Mousse) while Group B was used as a control group with no agent applied. Specimens of the two groups were subjected to a 10 days pH cycling model. The effect of CPP-ACP paste in preventing demineralization and promoting remineralization was evaluated by recording the changes in the microhardness values of the specimen’s surface enamel. Results: The results of the present study showed that both the Tooth Mousse and the control group showed reduction in the microhardness mean valuesof the enamel surfaces after ten days pH cycling. However specimens of group A (Tooth Mousse) recorded a lower reduction in microhardness mean value than obtained with the control group (Group B). Conclusions: The present study showed that the triple daily application of the CPP-ACP paste as a topical Coating for ten days had a significant effect in reducing demineralization of the enamel surface. Recommendations: It is recommended that CPP-ACP should be used as a self-applied topical coating after teeth brushing by children who have a high caries risk.