Police were called to Saint Cyprian Children's Center at 6223 Cedar Avenue in Cobbs Creek around 9:20 a.m. Tuesday for reports of the boy acting out of character.
Police were also told he had something hiding in his pants pocket.
Officer believed the boy was a hiding a toy, but once he took the item out it was discovered he had a clear plastic baggie containing 22 purple zip lock bags of crack cocaine.
None of the other children were exposed to the drug, police confirmed.
The boy told the teacher that the person who gave him the crack told him to keep it hidden, police said.
The preschool and kindergarten sit on the property of St. Cyprian Parish.