John Hooper, 71, of Eastbourne, raped the child when she was just eight years old between 2000 and 2001.
Hooper, of Upperton Gardens, was jailed for 12 years, plus a further four years to be served on extended licence. He will have to serve eight years before being considered for early release and will be a registered sex offender for life.
Detective Constable Jess Langlands said: “It took great strength for the victim to come forward last year, even after all this time, she just felt she had to report to us for the first time the horrendous abuse she had suffered.
“Hooper came to know this vulnerable young girl through friends, and unbeknown to anyone else he systematically abused her in private for his own sexual gratification.
“Anyone who has concerns about sexual offending against children can contact us at any time online or by calling 101, and can arrange to talk in confidence to experienced investigators.”
