Judge Rick West sentenced Gianforte to a 180-day deferred sentence, 40 hours of community service, 20 hours of anger management and a $300 fine along with a $85 court fee.
West originally sentenced Gianforte to a four days of jail time, to be completed in part through a work program, but switched instead to the hours of community service and anger management as those guilty of assault charges are ineligible for the work program.
A misdemeanor assault conviction in Montana carries a maximum penalty of up to six months in jail and a fine of up to $500, according to the state government website.
Gianforte has apologized to the journalist, Ben Jacobs, and also pledged to donate $50,000 to the Committee to Protect Journalists, an organization that promotes press freedom, "in the hope that perhaps some good can come of these events."
The encounter happened on May 24, when Gianforte was charged with misdemeanor assault
after Jacobs accused the politician of "body slamming" him at a campaign event.
Gianforte, a Republican, won the election the next day and apologized to the reporter during his acceptance speech.
He also issued a letter to Jacobs last week.
"My physical response to your legitimate question was unprofessional, unacceptable, and unlawful," Gianforte said in the letter.
"I made a mistake and humbly ask for your forgiveness."
Jacobs accepted the apology.
Jacobs was present and made a statement in the courtroom. Gianforte later asked if he could address Jacobs directly and apologized again.
"I just want to say I'm sorry and if and when you're ready, I look forward to sitting down with you in DC," he said.
During their encounter at Gianforte's campaign headquarters in Bozeman last month, Jacobs had been asking the then-candidate about the Republican health care plan when the assault took place.
Gianforte's campaign initially blamed the altercation on Jacobs' "aggressive behavior" and offered a version of events at odds with an audio recording and witness accounts.
In his letter, Gianforte stated: "I had no right to respond the way did to your legitimate question about health care policy. You were doing your job."
Throughout the proceedings, Rich said he was trying to give Gianforte the same sentence he would give anyone who plead guilty to attacking someone unprovoked.