De Blasio announced Daniel Nigro's (NEYE'-grohz) appointment Friday at a fire academy ceremony.
Nigro helped rebuild the Fire Department of New York after the Sept. 11 terrorist attacks. The attacks killed 343 FDNY members, and hundreds more retired in the following months.
After the attacks Nigro was named chief of department, the FDNY's highest-ranking uniformed post. He retired in 2002.
De Blasio and Nigro vow to work on diversifying the FDNY, which is nearly 90 percent white.
De Blasio is a Democrat who took office in January. He says outgoing Commissioner Salvatore Cassano wasn't considered a candidate to stay on.
The FDNY has 10,000 firefighters and 3,000 emergency medical service personnel.