Thousands of workers will strike between 11.30am and 4.30pm, the United Workers Union said, with rallies happening in Brisbane and Perth.
It will affect more than 120 facilities and almost 10,000 aged care residents across the two states.
South Australian aged care workers were also planning industrial action today, but it has been delayed after Anglicare and Southern Cross Care made an application to the Fair Work Commission.
The strikes in Queensland and Western Australia have been limited to five hours so workers in the affected facilities can prepare lunch and dinner for residents.
In a statement, UWU Aged Care Director Carolyn Smith said aged care workers had been pushed to do double and triple shifts, "facing dire conditions in PPE (personal protective equipment) and no let-up in sight in many facilities".
"But COVID was just the latest burden in an aged care system already in crisis," she said.
"Aged care workers report aged care residents are frustrated, upset and humiliated as they wait too long to be showered, too long for soiled pads to be changed and too long, sometimes, even to be fed.
"All this, while aged care workers earn some of the lowest wages in Australia."