Objective: The aim of this study was to evaluate the remineralization effect of Casein Phosphopeptid Amorphous Calcium Phosphate (CPP-ACP) on white spot lesions (WSL) and its inhibitory effect on Streptococcus mutans colonization. Study design: The study group consisted of 60 children exhibiting at least 1-WSL. Subjects were randomly divided into 2 groups: a test group of using CPP-ACP cream (Tooth Mousse, GC Europe N. V. Leuven, Belgium) and a control group using only fluoride containing toothpaste for a period of 3-months. Baseline WSLs were scored using DIAGNOdent device (KaVo Germany) and the saliva samples were collected to measure S. mutans counts. After the 3-month period the WSLs were again recorded and the saliva sample collection was repeated. Wilcoxon Signed Ranks Test was used for statistical analysis. Results: DIAGNOdent measurements were increased by time (p=0.002) in control group and no statistically significant difference (p=0.217) was found in test group by the 3-month period. In both groups, the mutans counts were decreased in 3-month experimental period. Conclusions: These clinical and laboratory results suggested that CPP-ACP containing cream had a slight remineralization effect on the WSL in the 3-month evaluation period however longer observation is recommended to confirm whether the greater change in WSLs is maintained.