The flames broke out around 6:30 a.m. on the 1500 block of North Gratz Street.
Crews who arrived within minutes of the call were quickly informed a boy was trapped on the third floor of the row home.
Neighbors say they woke up hearing screams and the sounds of fire trucks racing onto the block.
"I hear, 'Get out the house! Get out the house.' And I smell smoke," recalled Kareema McGoone.
"You could see the flames from the side because it was directly next to me," said Regina Fiore.
Firefighters say it was a dangerous fire to fight.
"It was extremely heavy conditions, smoke conditions, a lot of heat," said Battalion Chief Brandon Wilson.
As firefighters fought the flames, additional crews ran into the home where they found the 5-year-old boy and carried him outside.
"We launched an aggressive interior attack, which we normally would do if we're able to due to report of people being trapped. It was pretty quickly at that point. Honestly, as fast as it could've happened," said Wilson.
Medics took the boy to the Children's Hospital of Philadelphia in critical condition.
A 38-year-old woman was also hurt in the fire and was taken to Temple University Hospital.
Neighbors say they all hope the young boy will pull through.
"Still just worried for the boy, just worried," said McGoone.
The fire marshal's office is still investigating the cause.