Douglas Hammersley was given a two-year suspended sentence after pleading guilty to three counts of indecent assault.
The Crown Prosecution Service said the incidents took place in the Buckinghamshire area, to the west of London, when the victim was between five and eight years old.
“We were able to prosecute Hammersley thanks to the victim coming forward, even though the offences were committed more than four decades ago,” said Jennie Laskar-Hall, senior prosecutor for the CPS.
In December, a 101-year-old man was jailed for 13 years for a string of historical sex crimes against two young sisters and their brother. Police said he was the oldest person to have been found guilty of a crime in British legal history.