Hafeez resigned as Pakistan's captain in the shortest format of the game following the country's exit in the group stages of this year's World T20 in Bangladesh.
And the Pakistan Cricket Board (PCB) announced on Tuesday that veteran all-rounder Afridi has taken over and will skipper the side in India in two years' time.
Misbah-ul-Haq, meanwhile, has been retained as Pakistan's Test and one-day captain ahead of next year's ICC World Cup.
PCB chairman Shaharyar Khan commented: "In line with my policy of taking decisions democratically, I consulted the Cricket Committee and board members before announcing these decisions.
"I wish both Afridi and Misbah very good luck in their upcoming assignments."
Afridi, who has played 74 T20s and 381 ODIs for Pakistan, took to Twitter to express his delight at being handed the role.
"I am honoured to be given the chance to lead my country and will do my best always, thanks to all for your messages," he wrote.
Afridi was previously removed as captain of his country in 2011 following a falling out with coach Waqar Younis.
His first game as T20 skipper comes against Australia in Dubai on October 5.