Major dairy companies have reassured customers there will be minimal production disruptions when 1400 workers walk off the job for better pay and conditions.
Processing workers from Saputo, Fonterra, Peters and Lactalis will strike for 48 hours from Wednesday.
The United Workers Union says the companies have refused to offer fair wages and improved working conditions for their Victorian workers amid rising living costs.
"Workers don't make this decision lightly," national secretary Tim Kennedy said.
"They're not even asking for a wage increase that matches inflation, just five per cent or so that gets them a little closer to being able to keep up with skyrocketing costs."
Along with the wage increase, workers want personal leave accommodating their 12-hour shift pattern and community service leave for helping in natural disasters.
The union has acknowledged the industrial action will lead to disruptions for the dairy sector.
But Mr Kennedy said the dairy companies were vital to many regional Victorian communities, so the strike was necessary.
"It's about safeguarding the heartbeat of our regional communities," he said.
Fonterra director Rob Howell said the company had a "fair and reasonable offer" on the table for workers, with a minimum 10.5 per cent salary increase over three years and more leave options.
Fonterra would ensure there were minimal disruptions from the industrial action, he said.
"Our farmers will continue milking and we will be doing everything we can to ensure that their precious, perishable milk can be collected and not wasted," Mr Howell told AAP in a statement.
Saputo was committed to resolving outstanding items with union representatives "amicably and swiftly", operations director Gerard Lourey said.
The company is also putting contingency measures in place to minimise disruptions.
Lactalis said its priority was working with farmers, who were at the peak of the spring milk season.
"We will do everything within our power to ensure action by the United Workers Union and the Australian Manufacturing Workers' Union does not result in farmers having to dump milk," a company statement to AAP read.
A Peters spokesman said the company was surprised by the "unnecessary union-led blanket action" and negotiations have continued in good faith.
"Peters offers the best employment conditions in the ice cream industry, paying its factory workers 70 to 80 per cent above award," the spokesman told AAP.
