The attack happened in the back of the 4600 block of Rosehill Street in the Feltonville section on the morning of June 13th.
It was around 4:30 a.m. when, police say, the girl was dragged from her bedroom by a naked man who took her to a nearby alley and sexually assaulted her.
Police say the parents heard screaming, but the child had a history of sleepwalking and nightmares so they were accustomed to it.
According to authorities, the suspect told the victim to go home after the attack.
The assailant is described as an adult black male, 6 feet tall with a thin build and clean shaven. He was wearing a green mask that partially covered his face up to his eyes, grey sweatpants, black t-shirt and black Nike low top sneakers.
Officers say they've made progress in the case but need help tracking down the suspect.
If you have any information, you're asked to call Philadelphia Police at 215-686-TIPS (8477) or through phillypolice.com.