Sussex Police said Gary Fenn, 50, of Saxon Road, Saxmundham, Suffolk, was already a registered sex offender when he travelled more than 150 miles to prey on the young girl, who was under the age of 13.
He appeared in custody at Hove Crown Court on Friday (November 5).
He was convicted of sexual assaulting the girl and of two breaches of Sex Offender Registration Notification requirements.
A police spokesperson said: "[He] was given a nine-year extended sentence, comprising five years imprisonment and four extended period on prison release licence."
Fenn will also continue to be a registered sex offender for life and was given a Sexual Harm Prevention Order (SHPO) to last indefinitely, severely restricting his access to children and digital communication devices.
Emily Turner, Detective Constable of the West Sussex Safeguarding Investigations Unit, said Fenn had previously been convicted of offences involving indecent images of children.
She said Fenn, in June this year, used a dating website to get to know a woman and travelled to Southwick in Sussex to meet her.
"He used this opportunity to meet and sexually touch her young daughter," DC Turner said.
"However the girl quickly escaped the situation and informed her mother who then contacted the police.
"We swiftly investigated and arrested Fenn who was then charged on the authority of the CPS."
Fenn has been in custody ever since his arrest, DC Turner said.
She added: "The bravery of this young lady in standing up against what she knew to be wrong and by supporting this prosecution has undoubtedly kept other children safe from this predatory paedophile who has previous convictions for sexual offending."
In sentencing him, Judge Shani Barnes said: "We cannot underestimate the damage caused to the family by Fenn taking this opportunity to offend."
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