The Liberal candidate and former Australian ambassador to Israel is the first Indian-origin lawmaker in the country's Parliament after winning a seat in Sydney suburb.
Around 16 million Australians swarmed to the polling booths across the country on Saturday to elect the nation's 31st prime minister, in what was widely referred to as the climate-change election.
The conservatives became a rare minority government after they dumped Malcolm Turnbull for Morrison in an internal power struggle last August.
Steggall said earlier Saturday she believed she could win and was running in the election to give locals a choice.
Shorten has been campaigning hard on more ambitious targets to reduce Australia's greenhouse gas emissions.
Opposition leader Bill Shorten had said Saturday morning that he was confident Labor would win, but Morrison would not be drawn on a prediction.
In just 48 hours on the campaign trail this week, Australia PM Scott Morrison travelled 8,000 kilometres.