Ryan Walsh, of HMP Doncaster, was found guilty of seven counts of sexual assault following a trial in August this year and was today (Thursday) sentenced at Sheffield Crown Court.
The charges relate to two teenage girls, who cannot be named for legal reasons, who were under 16 at the time of the offences.
The jury heard how Walsh, formerly of Bowden Wood Road, Sheffield, befriended his victims and forced them to commit sexual acts.
Walsh, 29, is already serving a custodial sentence for sexual offences, which he pleaded guilty to in November 2015.
That same month, concerned parents came forward to police to report that they believed Walsh had abused their child and a new investigation began.
PC Andrew Parker, the investigating officer, said: “Walsh has shown no remorse for his actions and subjected his victims, who have both been so brave, to the anguish and distress of a trial.
“They and their families have had to go through this ordeal and I am pleased he was found guilty of these awful crimes.
“I hope that with sentencing today they can begin to rebuild their lives knowing he is behind bars.”