Hawks CEO Steve Koonin made the announcement Tuesday, also declaring Sept. 1, 2015, as Dikembe Mutombo Day.
Mutombo, who was surprised by Koonin's announcement, teared up when he heard the news.
"The most surprising, as you can see from the tears in my eyes, is the announcement that was made," Mutombo said, according to the Atlanta Journal-Constitution. "It's the most shocking to me. ... I didn't know the Hawks were going to retire my jersey. I can't believe it. It's going to be a great day."
Koonin said few players matched the impact Mutombo made "as a player, man and humanitarian.''
Mutombo, who played for the Hawks from 1996 to 2001, will be enshrined in the Naismith Memorial Basketball Hall of Fame on Sept. 11. He ranks third in franchise history in blocked shots and rebounds per game. He ranks second in NBA history in blocks.
Mutombo's jersey number will be the fourth retired by the franchise. Bob Petit (No. 9), Dominique Wilkins (No. 21) and Lou Hudson (No. 23) also have had their numbers retired.
The Associated Press contributed to this report.