"The tribunal has taken the decision with a clear conscience and under no pressure from either the board or anyone else," tribunal head Justice Aftab Farrukh told in a news conference. He also told that the three-member tribunal felt the original punishment was too harsh.
"We also took into consideration the past record of Shoaib and that he had publicly apologised for his behaviour and past deeds," Farrukh said.
"He has promised to reform himself and we have also recommended to the board that he should be given proper counselling."
Akhtar, who has played 46 Tests and 138 one-day internationals since 1997, was banned in April following a series of disciplinary violations, including his public criticism of the PCB in January after he did not make a short-list of 15 players who were offered a central contract.
Akhtar was already on two years' probation for hitting teammate Mohammad Asif with a bat days before the Twenty20 World Championship in South Africa last September.
His lawyer Abid Hasan Minto said the player had the right to pursue an appeal against the 18-month ban.
"But we will take a decision after going through the long and detailed order of the tribunal," Minto said.