David Kendrew, 54, of New Winterwell, Wath-upon-Dearne, groomed one of the victims, "a vulnerable young girl", bribing her with cigarettes and alcohol.
He pleaded guilty to indecent assault on a child, four counts of sexual activity with a child, one count of sexual assault and one count of rape. The charges date back to 1976, with the most recent occurring in 2013.
An investigation was launched after one of the victims came forward to report the abuse she suffered by Kendrew in April last year, Sheffield Crown Court heard yesterday.
As a result of information obtained during the investigation, two other victims were identified.
He was arrested in April last year and pleaded guilty to all seven charges at earlier hearings.
The investigating officer in the case, Detective Constable Rachel Morton, of the Rotherham Child Abuse Investigation Team, said: "The three victims involved in this case have shown remarkable courage in coming forward and reporting the abuse they suffered at the hands of Kendrew.
"The bravery and patience they have shown throughout the process has been commendable and I hope they can feel reassured knowing that Kendrew is now behind bars."
Sentencing Kendrew to 12 years in jail, Judge Simon Lawler said: "This was the grossest abuse of trust of a vulnerable young girl, you groomed her from the start and later with bribes of cigarettes and alcohol.
"She submitted over the years as she did not know better, it was a way of life for her and she acquiesced.
"This was purely for your own sexual gratification. I am told the victim has not let this ruin her life which is great fortitude and courage on her part."