The 32-year-old man, whose trial gripped the Esgenoopetitj First Nation and the province, was convicted of first-degree murder in the death of Hilary Bonnell.
The CBC's Jennifer Choi, who was in the courtroom just before the verdict was read, described the atmosphere as tense as both Curtis Bonnell and Hilary Bonnell's family members awaited.
Hilary's family cried out loudly upon hearing the verdict, with applause ringing out in the courtroom in Miramichi.
Pam Fillier, Hilary's mother, began to sob and cry.
She stood up and clapped her hands and then thanked the jury as they walked out of the room saying, "God bless you, thank you."
Afterward, Hilary's family gathered outside of the courthouse.
"I was so nervous. I was terrified he wouldn't get first [degree murder]. I'm glad he got first," a shaken Fillier told reporters.
Fillier said this is the beginning of closure and that she can finally start to move on with the rest of her life.
But while Bonnell will spend a minimum of 25 years in prison, she doesn't think she will ever completely heal after losing her only daughter.
"We could say 'guilty, guilty' till the end of time and she won't come back," Fillier said.
Boyd Bonnell, Hilary's father and Bonnell's uncle, said his family has been ripped apart.
"It's been very difficult. It's even been more difficult that it's my nephew.... He's gotta do the consequences of his actions," he said.
Curtis Bonnell's lawyer, Gilles Lemieux, said his client is disappointed.
"He's run the gamut. He was shocked. We prepared him: 'You have to expect the worst and hope for the best,' " Lemieux said.
Hilary was 16 when she died in 2009. Her disappearance from the Esgenoopetitj First Nation on Sept. 5 of that year sparked an extensive search.
Her cousin, arrested two months later, was accused of holding her against her will, sexually assaulting her and killing her.
Evidence at the trial showed Curtis Bonnell had told police, his father and a Esgenoopetitj First Nation spiritual elder that he had killed her. But the defence maintained the confession to police was given under pressure.
Two months later, Bonnell led police to a wooded area where he said he buried Hilary's body.
The jury gave its verdict on its second day of deliberations.