Mitchell, 29, of Pittsburg, was convicted of bludgeoning Keller with an aluminum softball bat at her Diablo Court home in Novato on July 12, 2009, the child's first birthday.
He was arrested several hours later in Citrus Heights, Calif., and the couple's daughter was found safe in his car.
Marin County Superior Court Judge Kelly Simmons sentenced Mitchell to 26 years to life for first-degree murder and use of a weapon, and nine years for domestic violence battery and kidnapping.
Mitchell addressed the court this morning, again denying he killed Keller. He called the case "a big circus from day one."
He said he felt unfairly put in the spotlight because of his association with the Mitchell Brothers' porn empire.
"It was nothing but poison in the water and a flock of sheep running over a cliff at the sound of 'James Mitchell,'" he said. He said he never wanted any part in the family business. "I was just born with my father's name," he said.
Mitchell said he still loves his daughter and Danielle. He testified during the trial that two other men were at the Novato home when he arrived there for his daughter's birthday party on the day of the murder, and said they were responsible for the killing.