Mark Andrew Richmond, aged 27, of Whitcomb Drive, Rossington, pleaded guilty to sexual activity with a child after a police probe was launched in December when his victim's family raised concerns.
Detective Constable David Whitehouse, from the Doncaster Child Abuse Investigation Team, said: “This has been a complex investigation and I commend the victim in this case for her strength throughout our inquiry.
“Richmond has accepted responsibility for his vile crime and this result shows that we will continue in our relentless pursuit of sexual offenders to protect children and young people from harm.
“I hope this case acts as further encouragement to victims and survivors of sexual exploitation that we investigate these matters thoroughly, and will do whatever we can to bring perpetrators of abuse before the courts.”
Richmond has been placed on the Sex Offenders Register.