Aamir, 23, returned to the Pakistan squad for the limited-overs away series against New Zealand, completing a cycle of redemption following his spectacular fall from grace in the 2010 spot-fixing scandal.
"We now need to move on and I will back Aamir and expect him to serve Pakistan cricket with total dedication and commitment," Afridi wrote on his twitter handle.
The star all-rounder added, "Happy to have Aamir back in the team."
"He admitted his mistake and we should back him now."
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Aamir, who served a five-year ban and jail time for indulging in spot-fixing during the 2010 tour of England, was expected to make the squad after being brought back into the national camp despite resentment by fellow players.
Afridi, however, added he respected the stance taken by some players on Aamir's return to the team, including teammates Azhar Ali and Mohammad Hafeez.
"I respect Azhar and Hafeez's stance. We suffered a lot due to spot-fixing scandal and our image was tarnished everywhere," he said.
"Aamir spoke the truth both to courts and the Pakistani public, unlike the rest who kept lying for two-three years," he added.
Afridi said that former players, critics and fans should back Aamir when he returns to the field.