Hospitality Union 'United Voice' mounted the appeal to keep workers' penalty rates for Sundays and public holidays unchanged, after the first round of cuts came into effect last weekend.
News of penalty rate cuts were a blow for pub worker John Keily, who sacrifices family time to work every Sunday.
He says so far, he's managed to get by financially, but now it might not be for long.
"Initially I stand to lose around 500 a year, but by the time the cuts come in fully, I'll probably be out of pocket $2,300 and that's a lot of money to me."
Once the cuts are fully introduced in 2019, the 73 year-old looks at losing around $40 a week.
Earlier this year, the Fair Work Commission decided Sunday rates be cut in the fast food, hospitality, retail and pharmacy sectors from July 1.
But the cuts won't be fully implemented until 2019 or 2020, depending on the industry.
Jess Walsh from hospitality union United Voice says they're arguing the Commision's decision failed to take into account the impact on low paid workers.
"These are minimum-wage workers who are today on about half the average wage. The cut to their penalty rates brought down by the Fair Work decision is about $2,000 a year and it's a pay cut they can't afford and they don't deserve."
Ged Kearney is from Australia's top union organisation, the Australian Council of Trade Unions.
She's vowing to fight until the decision is reversed.
"If our laws, the laws of this country, do not protect the living standards of Australians, do not uphold the incomes of the lowest-paid people in this country, then those laws are broken and those laws need to be changed. So we are challenging that, we are testing that through this appeal."
James Pearson is the Chief Executive of the Australian Chamber of Commerce and Industry.
He says the union's campaign is scare-mongering and ultimately holding Australian businesses back.
"A modest reduction in penalty rates on Sundays gives business, particularly small business, a chance to compete, a chance to open their doors for longer and provide more jobs and more work for Australians who want to do that."
In the meantime, Jess Walsh from the hospitality union United Voice remains hopeful that not all employees will be hurt.
"We are also calling on employers today to do the right thing by their weekend workers, to respect the contribution that they make and to maintain penalty rates for their weekend workers. Dozens of employers around the country, large and small, have decided to do that and we encourage other employers to follow suit."
But an uncertain future looms for some, like pub worker John Keily.
"What do I do? Fully retire? I probably will, that's a decision I'll have to make, but hopefully today this action before the courts is successful and everything is overturned but we'll just have to wait and see."
The next hearing is scheduled for September.
