It comes as support for the sector has turned into a key issue for Labor and the Coalition in the federal election.
With entry-level personal care workers currently paid as little as $21.96 per hour, the union says the case, which begins on Tuesday, will seek to lift wages to around $29 per hour.
HSU National President Gerard Hayes said, "Aged care workers have endured horrendous working conditions over the last five years".
"The funding is just not there to support the level of care older Australians deserve."
Mr Hayes said the aged care workforce has been carrying the "cost of a callous, tight-fisted (NSW) government that simply doesn't care" for far too long.
"This case is about rebalancing the scales and giving the long-suffering aged care workforce the decency and dignity, it deserves."
It follows the findings from the Aged Care Royal Commission's interim report which determined the sector was "undervalued, understaffed and under-resourced".
"Aged care workers have strived to provide care, but they've been hopelessly understaffed and worked long stretches without access to vaccines or protective equipment," Mr Hayes said.
Seeking to lift wages for personal care staff, caterers, cleaners, administration officials and other sector staff, the legal fight comes after health workers walked off the job earlier this month calling for a wage increases of 5.5 per cent, along with better working conditions.
Hearings for the case will be held in Sydney.
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