The industrial action is set to begin on Wednesday, targeting large dairy companies such as Saputo, Fonterra, Peters and Lactalis.
United Workers Union National Secretary Tim Kennedy said the decision followed the refusal to offer fair wages and improve working conditions amid rising living costs.
"Dairy workers have been dedicated, especially during the pandemic, with some even agreeing to wage offers as low as 1.5 per cent to support their companies," he said.
"But with the soaring cost of living, they believe it's time for change.
"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."
Kennedy said workers didn't make the decision "lightly".
Workers say while milk prices have surged, benefiting farmers and boosting profits, the workers processing the milk have yet to see their share.
"This is more than a wage tug-of-war; it's about safeguarding the heartbeat of our regional communities," Kennedy said.
Saputo told 9news.com.au it was committed to "negotiations to reach an agreement for our valued workers".
"We are focused on collecting and processing every litre of milk possible and are working collaboratively with farmers and industry to ensure we have a home for suppliers' milk during the industrial action," said Gerard Lourey, Saputo's Director of Operations.
"We are also actioning contingency measures to minimise business disruptions and keeping our customers, business partners and farmer suppliers updated on any temporary impacts they may experience."
Fonterra said it was disappointed that the UWU had encouraged industrial action, but respected the rights of those who chose to strike.
"We have mobilised a cross-company team to ensure that there are minimal disruptions as a result of this industrial action," Fonterra said.
"We have a fair and reasonable offer on the table that would mean better pay, more leave options and greater protections for our workers, who currently receive more than 30 per cent above the award wage.
"Our sincere thanks go to our dedicated team who will be taking on additional responsibilities during this time. Their commitment to our customers and our business is greatly appreciated."
Lactalis said it expected some delays to milk collection but would do everything in its power ensure the action would not result in farmers having to dump their milk.
"Lactalis has and will continue to negotiate in good faith with the unions to achieve a fair and equitable outcome," the company said.
"We believe the four-year deal we have tabled at Longwarry is very fair given the current industry pressures, providing certainty and security for our employees."
Peters has been contacted for comment.
