Grahame Humphries abused his position within the Anglican Church by kissing and touching the teenager, whose family had been looking after him while his wife was away, Kingston Crown Court heard.
His wife was pregnant with their child at the time of the offence.
Mr Humphries, 71, was sentenced to eight months in prison, suspended for two years, after admitting to indecent assault against the girl between 1971 and 1972.
Humphries, who has worked in parishes across England until 2012, was also ordered to pay £500 in costs, given a 24-month supervision order and told to sign the sex offenders register for the next five years.
His victim came forward after seeing that survivors of serial paedophile Jimmy Saville were being listened to.
Judge Paul Dodgson told the pensioner: "Forty-five years ago when you were a young curate aged 27 you did something very wicked.
"You took advantage of your position of trust to a girl then aged 14."
