The case is linked to the illegal selling of state gifts.
According to the PTI media team, the verdict also bars Khan from holding public office for 10 years.
It comes a day after Khan was handed a 10-year prison term for revealing state secrets in a separate case - and a week before national elections.
Khan's media team called it "another sad day in our judicial system history", saying:
"No cross questioning allowed, no final argument concluded and [the] decision pops up like a pre-determined process in play."
The team said they will appeal the ruling.
In August, Khan was already sentenced to three years behind bars by another court for selling expensive gifts owned by the state that he received during his 2018-2022 premiership.
Wednesday's verdict was linked to the same matter.
This time, it followed an investigation by the country's top anti-graft body, which also charged his wife, Bushra Bibi, in the case.
PTI said she was arrested shortly after the verdict.
A prosecution team member, who asked not to be named, confirmed the verdict to Reuters.
Local media said it also came with a hefty fine.
Khan has said that he legally purchased the state gifts.
His earlier three-year sentence was suspended, but the 71-year-old remains locked up in connection with other cases.
