The decision comes two days after the young Dutchman pleaded guilty to killing Stephany Flores and at a moment when the family of U.S. teenager Natalee Holloway is renewing efforts to bring him to the United States to face charges related to her 2005 disappearance.
The court also ordered him to pay $75,000 in reparations to the family of the 21-year-old victim. He said he reserves the right to appeal.
The prosecution had sought a 30-year sentence for first-degree murder and theft.
Under Peru's penal system, Van der Sloot could become eligible for parole after serving half of the sentence with good behavior, including work and study.
Van der Sloot's lawyer argued that client killed the 21-year-old Flores in May 2010 during a fit of rage he blamed on psychological trauma from being hounded as the prime suspect in Holloway case.
The Holloway case remains open and her parents want Van der Sloot to eventually be extradited to the U.S. and tried on related charges. He has been indicted in extortion charges there for allegedly offering to lead a lawyer for Holloway's mother to her daughter's remains.
Van der Sloot long ago confessed the Flores killing, telling police he became enraged after the business student discovered his connection to the Holloway disappearance on his laptop while they played poker online. Police forensic experts disputed that version, and the victim's family said Van der Sloot killed Flores in order to rob her.
The prosecution maintained Van der Sloot killed Flores with "ferocity" and "cruelty," concealing the crime and fleeing to Chile, where he was caught two days after Flores' decaying body was found.
He took more than $200 in cash plus credit cards from the victim and made his initial getaway in her car, leaving it in a different part of Lima, prosecutors say.