Mayor Cory Booker said he came home Thursday night to find the woman's home engulfed in flames.
A woman was screaming that her daughter, Zina Hodge, was still inside. Against the wishes of his security detail, Booker went in and looked for Hodge, who was trapped in a second-floor bedroom.
The mayor said he heard Hodge screaming, "I'm here, I'm here, help I'm here." Booker, who is 6-foot-3, found Hodge and threw her over his shoulder.
The 42-year-old mayor downplayed his actions, saying he just did what any neighbor would do.
"I didn't feel bravery, I felt terror," he said Friday at a news conference. "It was a moment I felt very religious, let me put it that way."
Booker was taken to a hospital to be treated for smoke inhalation and second-degree burns. He was later released. Hodge also suffered from second-degree burns. She remains hospitalized in stable condition.
The exact cause of the fire was not immediately known, but investigators said it likely started in the kitchen.
The Associated Press contributed to this report.