Svein Ludvigsen, 72, a former fisheries minister, was convicted of abusing his position as county governor and exploiting the vulnerable situations of three young men, one of whom has a mild mental disability.
The sentence was handed down on Wednesday but made public a day later.
The abuse of the men, now aged between 25 and 34, occurred between 2011 and 2017, according to court documents seen by AFP.
Victims told the court that Ludvigsen, who is now retired, had offered them housing and jobs in exchange for sexual favours.
Two of the three men had also been concerned that their residency permits could have been withdrawn if they didn't comply.
Ludvigsen has always denied doing anything illegal.
During his trial, he admitted to having consensual sex with one of the victims on three occasions in Oslo.
Before becoming county governor, the former conservative politician held several senior national positions.
He was first arrested early last year and charged in November.
Ludvigsen's lawyer, Kai Vaag, told Norwegian media on Thursday that his client intended to appeal.