A video posted on the Instagram page @humansofeastwooddaily showed Abbott in a business shirt and tie holding open a boom gate and allowing motorists to exit the busy car park.
It is believed the car park was beneath the Theatre Royal Sydney on King Street, and the footage is actually from June.
At that time, the theatre was showing a 40th anniversary special of Cats the Musical.
A bottleneck was created in the car park as theatregoers all left at the same time, but Abbott decided to help out and ensure everyone was able to get home without much of a delay.
Abbott was a member for the Sydney electorate of Warringah between 1994 and 2019, and was leader of the Liberal Party between 2009 and 2015.
He led the party to a landslide win at the 2013 election, but lost the prime ministership in 2015 after being defeated in a leadership spill by fellow Sydneysider Malcolm Turnbull.
Abbott is also known to be a volunteer firefighter for the NSW Rural Fire Service.