Crews were called around 3:30 a.m. Thursday to the unit block of East Powell Street in Millville.
Arriving firefighters found the squatter, who had jumped from the first floor, suffering from lacerations and smoke inhalation.
Firefighters battled the fire for over an hour, officials said.
Assistance from neighboring towns was brought in as the fire reached two-alarms.
Officials are calling the fire suspicious in nature.
The squatter was taken to the hospital for treatment. No firefighters were injured.