Ryan Jason Hickey had previously pleaded guilty to aggravated assault.
He was sentenced in Grand Falls provincial court on Friday.
Hickey, who has been in custody since the attack on April 10, 2013, has four-and-a-half years left to serve.
He was also banned from possessing any weapons for life and ordered to provide a DNA sample.
Hickey was originally charged with attempted murder and aggravated assault in the attack on Donald Jaillet and pleaded not guilty.
A preliminary inquiry was scheduled to be held last month, but Hickey changed his plea to guilty of aggravated assault, and the Crown withdrew the attempted murder charge.
Jaillet was driving a bus from Moncton to Rivière-du-Loup, Que. when he was repeatedly stabbed by one of the eight passengers on board.
He narrowly escaped death, losing two-thirds of his blood from multiple wounds to his arm, abdomen, head and face.
But Jaillet, who was in critical condition and has required at least four operations, has said he bears no ill will toward Hickey.