Andrew Cairns, of Robinson Street, Fulwood, Preston, was originally accused of seven counts of sexually touching the youngster - including spanking her.
The 36-year-old was cleared of five charges but two guilty verdicts were returned following a trial at Preston Crown Court three weeks ago.
The jury was previously told the girl, who cannot be identified for legal reasons, had first made the claims to her mother during a caravan holiday but had initially retracted them.
However, she gained the courage to come forward again and pursue the charges at court.
The youngster had to come to court to give evidence against her attacker throughout the week long trial.
The girl’s father told the Evening Post they were frustrated Cairns had been sentenced without the family’s knowledge.
He added: “ The sentence is important because it shows that my daughter has been believed.
“She has been tormented by people calling her a liar and bullying her, but the jury found him guilty.
“She has been through a terrible ordeal.”
Judge Robert Altham, sitting at Preston Crown Court, imposed a 14 month prison term on each count, but ordered that they should run concurrently.