He was one of the firefighters sent to a real estate building on the unit block of West Kings Highway in Haddonfield.
A Delaware River Port Authority worker saw smoke coming from the Coldwell Banker office and called 911.
When firefighters arrived around 3:40 on Tuesday morning, they found flames spitting out of the attic.
The blaze quickly went to two-alarms.
The firefighter became ill while working on the fire.
He was taken to Our Lady of Lourdes Medical Center in Camden, where he was treated and released.
A second fireman was treated for a foot injury at the scene.
Crews placed the fire under control in about a half hour.
Investigators believe it was an electrical fire that started in the third floor bathroom.