The Canadian pop star appeared before an Ontario judge via video link from a lawyer's office in Los Angeles.
A dangerous driving charge laid in the case was withdrawn, Bieber's lawyer said, and the singer was sentenced to a $750 fine for the careless driving charge and an absolute discharge — guilty without the registration of a criminal conviction — on the assault charge.
"That brings to an end the incidents of Aug. 29, 2014 that led to the charges relating to the photographers in Stratford," Bieber's lawyer Brian Greenspan told The Canadian Press.
"The resolution was as a result of a thorough examination by the Crown, an evaluation that this matter was a very, very short-lived and spontaneous issue. It was a response to the invasion of privacy by the photographers involved."
Bieber had been arrested and charged in the case after a collision between a minivan and an ATV in a rural area northeast of Stratford.
His lawyers said Bieber was on a "peaceful retreat'' at the time with Selena Gomez — his on-again, off-again girlfriend — when it was disrupted by paparazzi.
Ontario Provincial Police had said the driver of the ATV and an occupant of the minivan "engaged in a physical altercation.''
Bieber's lawyer said the singer had simply been reacting to a "very, very upsetting situation."
"Mr. Bieber, more than anything has been able to retreat to his home in Stratford and to be with his family with whom he's very close, without his privacy really being invaded," Greenspan said. "The local community is very respectful of his privacy."
The assault charge that Bieber pleaded guilty to related to his interaction with a photographer, Greenspan explained.
"He came over to the side of the vehicle where one of the photographers was holding a large camera," he said. "There was some physical contact...it was described that Mr. Bieber was swinging at him, grabbing at the camera, that could have been three times at the most."
Greenspan added that the photographer involved in the incident was "twice the size" of Bieber and "simply deflected" attempts to hit him.
Greenspan also noted that photographers involved in the case had both pleaded guilty earlier to trespassing on Bieber's father's property near Stratford, and were fined.
Bieber's guilty plea on Thursday came just weeks before his case was set to go to trial.
In another Canadian case, Bieber was charged with one count of assault in connection with an incident involving a Toronto limousine driver in December 2013.
Prosecutors withdrew that charge last September saying they didn't see a reasonable prospect of conviction.
Bieber still faces a civil lawsuit in relation to the incident, with the limo driver seeking $850,000 in damages.
The driver alleges he was "viciously assaulted" by Bieber, but the singer claims the allegations were made up by the driver in the hopes of getting a hefty payout.
None of the allegations have been proven in court.