Former Twenty20 captain Mohammad Hafeez and current one-day captain Azhar Ali had boycotted the camp on Thursday, refusing to train alongside Amir, who was jailed in 2011 for spot-fixing.
Pakistan Cricket Board (PCB) chairman Shaharyar Khan said Hafeez and Ali had now joined the camp.
“The matter has been resolved,” Khan told reporters.
“Both listened to me and agreed to join the camp unconditionally and will have to support Amir when he returns to the team.”
The training camp is staged to select the squad for next month’s tour of New Zealand where Pakistan play three one-day and as many Twenty20 internationals.
Hafeez, who in November spoke publicly against Amir, said he forgave him but was sticking to principle.
“My stance was based on principle and it was portrayed in a wrong sense,” Hafeez told reporters.
“My stance is the same against all players who stained Pakistan’s image through corruption.
“It’s my right to raise my voice, which I did, and I will do everything in my capacity to fight corruption,” said Hafeez.
“My stance is that all corrupt players should not be given another chance to represent Pakistan.”
Amir, then Test captain Salman Butt and Mohammad Asif were charged with accepting money in exchange for arranging deliberate no-balls during a Test match at Lord’s in England in 2010.
The three players and their agent Mazhar Majeed were jailed by a British court in 2011. Amir, Butt and Asif were also banned from cricket for five years.
But in September this year the International Cricket Council lifted sanctions against the three players. Amir’s ban was relaxed in January this year and he was allowed to play domestic matches.
At the time of the ban, Amir was tipped as one of the most talented fast bowlers in the world.
Since his return, he has taken 22 wickets in four non first-class games, while his tally of wickets in the qualifying rounds of the Quaid-e-Azam trophy stood at 34.
He also took 14 wickets in 11 Bangladesh premier league matches, forcing the selectors to chose him for the camp.
The Pakistan players are training ahead of the national side’s upcoming tour of New Zealand, where they will play three one-day internationals and three Twenty20 matches.
Butt and Asif will feature in the national one-day tournament next month, their first appearance in domestic matches since their ban expired.
PCB had given them a rehabilitation programme to undergo before qualifying for national selection — a process Amir has already completed.