The incident happened around 6:30 p.m. Friday in the 600 block of Taylor Court in Fox Hunter Crossing.
The child's mother told police her son was playing in a sand box when an unknown woman approached the fence.
Her son got up and walked over to the fence, and the mother saw the woman start to lean over toward the child.
The mom says she yelled at the woman to get away from her son. The woman then fled the scene in an older model red or maroon four-door vehicle with an unknown man.
The woman is described as between 40 and 50 years old, 5'07" with wavy brown shoulder-length hair. She was wearing a green raincoat and blue jeans.
The man is described as being between 50 and 60 years old with short white hair.
Anyone with information is asked to call police at 302-395-2782 or Crime Stoppers at 800-TIP-3333.