Flames broke out at the Novacare Rehabilitation Center at about 2:30 Saturday morning.
The center is on the 1000 block of Mill Creek Drive in Feasterville.
The blaze ripped through the building which is home to the rehab center and D and N Fitness.
The fire and the effort to put it out, has caused extensive smoke and water damage to the interior of the building.
There are no reports of injuries, and no word yet on the cause