Horry County police charged Christopher Revilla, 23, with Criminal Sexual Conduct with a Minor.
The mother of the 11-year-old girl told police Revilla would sometimes watch her children.
The daughter said he would come into the room where they were sleeping and touch her breasts and "other areas" below the waist, both outside and underneath her clothing.
The girl told police she would roll over and pretend to be sleeping.
Revilla was booked into J. Reuben Long Detention Center Tuesday.