Theodore Silcock was sentenced Friday for his conviction on a charge of first-degree sexual assault.
Silcock pleaded guilty to the charge last month. He was arrested in December after the girl's mother, who was dating Silcock, found pictures of her three-year-old daughter being assaulted.
Silcock offered an emotional apology in court, saying he had no excuse for his behavior.
He will be eligible for parole in 15 years. He will have to register with the state as a sex offender upon his release.