Kirkpatrick, 74, who starred in the Australian TV drama Prisoner Cell Block H, denied charges of gross indecency with a person under 16.
The court ruled on Thursday she had abused the 14-year-girl at her Melbourne home.
Kirkpatrick on Friday was sentenced to 100 hours of community service.
She will be placed on a sex offenders' register for eight years and has to undergo a sex offenders' programme and rehabilitation assessment.
In sentencing, Melbourne Magistrate Peter Mealy said Kirkpatrick would have been jailed if the offences were not historical in nature, local media said.
In a statement read to the court on Thursday, the unnamed victim said she had organised a meeting with Kirkpatrick through a TV producer while she was a patient in a psychiatric hospital.
She said she had not reported the abuse until recently because she feared people would call her "crazy".
Kirkpatrick played a warden called Joan, nicknamed the Freak, in Prisoner, a popular series set in a women's prison.
She later appeared in a host of other Australian TV shows and in 1991 played Marilyn's aunt Jean Chambers in Home and Away. Her most recent role was in a stage production of the musical Wicked.
Australian actress Maggie Kirkpatrick has avoided jail after being found guilty of sexually abusing a teenage girl in 1984.