John Nicolson, 23, was handed a sentence of four years and four months at Sheffield Crown Court.
He pleaded guilty to five counts of sexual activity with a child, two counts of causing a child to watch a sexual act, two counts of possession of indecent photographs of a child and one count of disclosing a private sexual photograph with intent at an earlier hearing.
Officers launched an investigation after concerns were raised by the parents of a 13-year-old boy about Nicolson’s inappropriate behaviour towards him.
South Yorkshire Police said that Nicolson had been using social media pages and an online dating app for more than three months to develop a relationship with the 13-year-old, lying about his own age and claiming he was 16-years-old.
He met up with the boy on several different occasions in Doncaster and sent presents - which police say expressed his feelings toward him - to the boy's home.
Officers arrested Nicolson at his home address in February and later charged him with the offences.
Detective Constable Richard Dickinson, who led the investigation, said: “Nicolson knew the age of his victim and intentionally continued to pursue and develop a relationship with him.
“His actions were for his own sick gratification and I would like to thank the victim for the bravery and courage he has demonstrated throughout both the investigation and the court process.
“I hope the young boy and his family feel some sense of justice has been achieved now Nicolson is behind bars for his despicable actions.
“We take any report of a sexual offence extremely seriously and I hope this investigation represents our commitment to thoroughly investigate all reports and protect victims of sexual abuse.
“If you have any concerns about someone you may know being a victim of child sex offences, please report it to police or anonymously through Crimestoppers.
“Everyone at South Yorkshire Police is committed to keeping our residents safe and we will work wherever possible to bring offenders to justice.”
Nicolson, of Gargrave Close, Doncaster, was sentenced on Friday.