The controversy is the latest to hit Sharif, an industrialist serving his third term as prime minister after the first two were interrupted by interventions from the country's powerful military.
The Supreme Court launched an investigation into the Sharif family's offshore wealth past year after opposition parties threatened to launch street protests.
The prime minister has insisted his father built up the family business before Sharif entered politics in the 1980s.
Hundreds of police officers surrounded the Supreme Court building as it delivered its highly anticipated verdict, and unauthorized people were barred from the area.
The final verdict is split 3-2 among the bench, with two dissenting notes in the judgment by Justice Khosa and Justice Gulzar.
Prime Minister Sharif's governement was sacked by then President Ghulam Ishaq Khan for alleged corruption in April, 1993.
It erupted with the publication of 11.5 million secret documents from Panamanian law firm Mossack Fonseca a year ago which documented the offshore dealings of numerous world's rich and powerful.
The JIT, which will have members from various government agencies, including the ISI, has been given two months to complete the probe into alleged corruption by the Sharif family.
Nawaz's staunch political opponent Imran Khan was present in the court when the verdict was announced. Sharif is seen as pro-business.
He had served as the Prime Minister from 1990 to 1993 and from 1997 to 1999.
"Two judges declared Sharif guilty and called for his disqualification", he added, but they were out-voted by "the three others who ordered further investigations".
She also posted another picture which showed the Prime Minister with Shahbaz Sharif, his daughter Maryam, Senator Pervaiz Rashid and other senior PML-N leaders.
Counsel for Prime Minister's sons Salman Akram Raja said that majority decision is the real decision of the court.
The leaked documents from the Panama-based law firm, Mossack Fonseca, had revealed the hidden offshore wealth of some of the world's top leaders and celebrities. Zardari also criticised Pakistan Tehreek-i-Insaf (PTI) Chairman Imran Khan for letting Sharif got off the hook through the judgement of the court.
Since the Panama Papers in June 2016, opposition parties have been jumping at the opportunity to register their protests and mobilise supporters to rally against Nawaz Sharif.