The 27-year-old was jailed for 30 months last November on charges of accepting corrupt payments during the Lord’s Test against England in August 2010.
He was freed on Thursday, according to his London legal company, 25 Bedford Row.
Butt’s father Zulfiqar said on Wednesday that he expected his son to be home within three or four days.
Butt, teammates Mohammad Asif and Mohammad Amir, and agent Mazhar Majeed were accused of arranging deliberate no-balls in return for money.
Amir was released in February after serving half his six-month sentence while Asif, jailed for 12 months, was freed in May.
The three players were banned for at least five years by the International Cricket Council (ICC), which has ordered the Pakistan Cricket Board to rehabilitate the former stars.
The trio has a right to appeal the ICC ban in the Court of Arbitration for Sports (CAS) in Switzerland. AFP