During proceedings in courtroom number 4 that lasted less than 10 minutes, the seven-judge bench headed by Justice Nasir-ul-Mulk announced the verdict and said Gilani`s sentence would last "till the rising of the court" or till the completion of the hearing.
The judges left the court immediately after announcing the verdict, effectively ending 56-year-old Gilani`s sentence.
However, legal experts were divided on whether Gilani`s conviction would lead to his disqualification. They said the court`s detailed order would provide clarity in this regard.
Emerging from the court, Gilani told the media: "We had sought justice. The decision was not appropriate".
The maximum sentence that could have been given to Gilani in this case was six months. . Earlier, Gilani drove in a small motorcade to the Supreme Court complex, where members of his council of ministers were waiting for him.
The premier then walked towards the building flanked by his son Abdul Qadeer Gilani and Interior Minister Rehman Malik as his supporters showered rose petals on him.
He stopped at the door of the building and waved to his supporters before going inside. The proceedings in the packed courtroom began at around 9.30 am.
After the judges entered the room, Gilani walked and stood at the rostrum with Law Minister Farooq Naek and his lawyer Aitzaz Ahsan. The government put in place strict security arrangements for Gilani`s third appearance in the Supreme Court in the contempt case.
Helicopters mounted aerial surveillance were also put in place while over 2,000 security personnel were deployed in the "Red Zone" where the apex court and parliament is located.
The Supreme Court has been pushing the government to reopen cases of money laundering against President Zardari in Switzerland since December 2009, when it struck down a graft amnesty (National Reconciliation Ordinance) issued by former military ruler Pervez Musharraf.
The government has refused to act, saying the President enjoys immunity in Pakistan and abroad.