The PML(N) supremo was however acquitted in another case connected with corruption.
The anti-corruption court found the ex-prime minister guilty in the Al-Azizia graft case but acquitted in him the Flagship Investment case.
The accountability court had earlier indicted Sharif for holding assets beyond his known sources of income last year in August.
Three cases - Avenfield properties case, Flagship Investment case and Al-Azizia steel mills case - were launched by the National Accountability Bureau(NAB) last year in September, following a judgment by the Pakistan Supreme Court that disqualified Sharif.
Sharif's supporters said the former prime minister would appeal.
"Appeal is our right, we will protest but will remain peaceful," former prime minister Shahid Khaqan Abbasi, who succeeded Sharif last year, told reporters outside the courthouse in Islamabad.
Sharif was sentenced in July to 10 years in prison by the same court, on charges related to the purchase of upscale apartments in London, after the Supreme Court removed him from power. He was released in September pending an appeal.
Reacting to the development, Pakistan's information minister Fawad Chaudhry said the "real face of Nawaz Sharif has been unmasked today",
Chaudhry added that the PML(N) leader was unable to provide the money trail for his assets, therefore, he was sentenced to seven years in prison.