The three-alarm blaze, which started after 5 p.m. in a building housing a fabric store, boutique and upstairs apartments, turned deadly when part of the roof collapsed, The Philadelphia Inquirer reported.
The dead firefighter was a captain. The other firefighter, injured in a rescue attempt, was hospitalized with burns. Neither victim was identified, the newspaper said.
Fabric store owner Bruce Blumenthal said he discovered flames when he went into the basement after smelling smoke. He said he tried to put the fire out with an extinguisher but it quickly spread.
Blumenthal said the fire appeared to have started in a wall and speculated it was electrical in nature.
The cause had not been confirmed.