Capt. Jack Ryan of the Philadelphia Police Department said the girl's body was partially buried and part of her head was exposed.
Detectives say the investigation began Monday when the caregiver of the 2-year-old reported her missing. She then led officers to Kemble Park.
They began to search for the girl early Tuesday morning before daybreak, using equipment like saws and shovels. Police brought in a cadaver dog who hit on something in a wooded area.
The body was discovered shortly before 11 a.m.
Police say the caregiver is a suspect.
"She was in the custody of this woman; the woman led us to the location where the child was recovered," Ryan said.
An autopsy will be performed to determine the cause of death. It is not yet known how long the child had been missing or her identity.