Jorge Renberto Ventura, 28, was convicted after assaulting a 13-year-old Marietta girl in her home in the summer of 2013.
Of the 50 year sentence, 30 years are to be served in custody, according to Cobb Superior Court Judge LaTain Kell.
Ventura will also be required to register as a sex offender.
The Marietta man was arrested in August and has since been held in jail without bond.
The victim testified she met Ventura on Facebook and he later came to her house on Aug. 5, 2013, when the assault took place, she said.
The girl said Ventura undressed her and touched her inappropriately. Her father came home during the assault, she said, and Ventura left by the back door of the home.
“This defendant gained the trust of this young girl, then used that trust to gain access to her home, and ultimately, her body,” Assistant District Attorney Susan Treadaway said. “There are no more despicable acts than these.”
During his sentencing hearing, Ventura said he was innocent and asked for mercy from the judge, according to a statement by the Cobb District Attorney’s office.
In 2010, Ventura was also convicted in Cobb County of terroristic threats.