Ceramide kinase (CerK) produces the bioactive lipid ceramide-1-phospahte and appears as a key enzyme for regulating cell growth and arachidonic acid metabolism. Although CerK is known to regulate cell migration, the precise mechanism is not fully understood. Lamellipodia is dynamic surface extensions of the cell which plays a pivotal role in cell migration. In this study, we focused the role of CerK on lamellipodia formation and cell migration. EGF is known to enhance the formation of lamellipodia. When A549 or MCF-7 cells were treated with EGF, CerK was colocalized with actin in lamellipodia. Knock-down of CerK enhanced the formation of lamellipodia in A549 and MCF-7 cells. Same results were shown in CerK knock-out mouse embryonic fibroblast cells. Transfection of CerK inhibited the formation of lamellipodia. Rac1 is known to drive the formation of lamellipodia. In A549 cells, knock-down of CerK enhanced the activity of Rac1 and translocation of Rac1 to the plasma membrane. Enhanced formation of lamellipodia by inhibition of CerK was attenuated by inhibition of Rac1 in A549 cells. Migration of A549 cells was also enhanced by knock-down of CerK, which was attenuated by inhibition of Rac1. These results suggest that CerK/C1P negatively regulates lamellipodia formation and cell migration via inhibition of Rac1 activity.