Mike Scott scored all 17 of his points during the Hawks' incredible second-quarter run, and the defense fended off the Pacers' frantic fourth-quarter charge to hold on for a 107-97 victory and a stunning 3-2 lead in the first-round series.
All the Hawks have to do is protect their home court and they will reach the second round for the first time since 2011, and throw the East into disarray after the talk all season was about an Indiana-Miami rematch in the conference finals.
Shelvin Mack led the Hawks with 20 points, while Paul Millsap had 18.
Paul George led the Pacers with 26 points and 12 rebounds.