Huon Aquaculture shareholders voted on Friday in favour of the takeover deal by Brazilian meat giant JBS.
Former critic of the deal and big shareholder Andrew Forrest eventually backed the deal.
The Foreign Investment Review Board has approved JBS' takeover plans last week.
Tasmanian-based Huon is Australia's second biggest aquaculture company.
JBS' original takeover offer of $3.85 a share valued the company at about $540 million, and Dr Forrest moved to block the bid by doubling its own Huon shareholding to 18.5 per cent.
On Friday his company voted for the share offer.
Share prices opened at $3.85 on news of the deal this week.
Huon chairman Neil Kearney said: "Today's overwhelming shareholder support for the JBS transaction will secure the future of Huon, the company's dedicated workforce and the hundreds of Tasmanian businesses that work with us."
One of the two proposed schemes of arrangement was supported by 99.77 per cent of votes cast and the other won 99.87pc of votes cast.
Mr Kearney on Monday said JBS had the skills and expertise to access new international markets for Huon products.
He told the annual meeting markets were starting to open up "as we see the beginnings of a cautious recovery from the worst of COVID" and "the building blocks are now in place to carry this business forward into the next decade and do so sustainably".
Huon made a $128.1 million loss for 2020-21, largely due to a $79.9 million impairment charge and lower prices.
JBS Australia chief executive Brent Eastwood said: "JBS Australia is pleased with today's outcome and appreciates the overwhelmingly positive shareholder response to our offer.
"Consistent with our acquisition track record in Australia, JBS will invest in the Huon business, its people and farming practices to support long-term sustainable growth.
"Acquiring Huon represents our first step into the aquaculture industry for JBS globally.
"We believe that our contacts and our ability to open up and access new markets, combined with the expert team at Huon, create a fantastic opportunity to take this business forward.
"We will uphold the highest standards for superior quality, fish health and sustainable farming practices, from water management to animal welfare, and stock densities.
"Over the coming weeks, JBS looks forward to engaging directly with Huon employees and, also, key Tasmanian environmental and government stakeholders."
Huon shares traded around $2.75 in the week before JBS made its first offer, which had support from Huon founders Peter and Frances Bender.
The price climbed to $3.83/share last week on the news of the FIRB approval.
After the Benders committed their shares to the Brazilians, JBS is understood to now hold at least 40pc of Huon, while another significant shareholder, Australian Super, has about 12pc.
Start the day with all the big news in agriculture! Sign up below to receive our daily Farmonline newsletter.