A Leeds Court judge jailed 71-year-old Zygmunt Misiekowski, formerly of Wakefield, after he was convicted of seven indecent assaults and one charge of procuring a woman to have unlawful sexual intercourse.
The offending took place in the Wakefield area and involved two victims who were both 12 when the Misiekowski abused them in separate incidents.
One victim reported that she met the suspect in 1985 when she was 12-years-old.
Leeds Crown Court heard that over a seven-year period Misiekowski groomed her, indecently assaulted her and procured her to have sexual intercourse with another man.
A second victim reported that she had been indecently assaulted by Misiekowski between 1991 and 1992.
Judge Tom Bayliss QC told Misiekowski, of no fixed abode, he was "a sexual predator of the worst sort."
Detective Inspector Vanessa Rolfe of Wakefield Police's child safeguarding team, said: “We wish to pay tribute to the bravery of both of these women who showed real strength and bravery in coming forwards and in supporting this prosecution.
“Their actions in reporting Misekowski’s offending to the police allowed us to mount an investigation and put a dangerous and predatory man behind bars.
She added: “Misiekowski’s behaviour in these offences was abhorrent. He sexually assaulted both of his victims, who knew him locally as ‘John Boy,’ and procured one of them to have sex with another male, causing further terrible harm to her.
“I hope seeing him receive such a substantial sentence will give now give them some sense of closure.
“We actively investigate all reports of none recent sexual assaults and would encourage anyone who has been a victim of an offence and for whatever reason may have not reported it at the time, to contact the police.”