Halifax man Shapoul Ali, 33, was more than double the girl’s age when he first met her after she had attended a school prom, a jury heard.
But Ali, who has been living at a bail address in Bradford, was said to have lied about his age and to have flattered the teenager until he had her in his clutches.
In her victim personal statement the teenager, who cannot be identified for legal reasons, said Ali turned her against friends who were against him and referred to his “manipulation” of her.
Shop worker Ali had denied four charges of sexual activity with a child, but he was found guilty following a trial at Bradford Crown Court.
He was cleared on a further allegation of perverting the course of justice.
Prosecutor Jayne Beckett said the case had involved in the use of alcohol by the defendant and she highlighted the considerable disparity in age between Ali and the girl.
Judge David Hatton QC imposed an indefinite restraining order which bans Ali from having any further contact with the girl and he also told the defendant that he would have to register as a sex offender with the police for the rest of his life.
The judge said Ali had engaged in sexual activity with the girl over a number of months.
“A prison sentence is inevitable for offences such as these which were repeated,” the judge told him.
“The legislation is there to protect young girls against the attentions of older men and it’s there to protect young girls against themselves and from being taken advantage of.”
Following the sentence, Detective Inspector Allan Raw, of Calderdale CID, said: “I would like to praise the victim for her bravery and courage in giving her evidence.
“We would always encourage victims to come forward knowing that they will be taken seriously, treated sensitively and that we will take action to bring offenders to justice.”