Officials at the food manufacturer, which owns brands including Goodfella's Pizza and Fox's, say they regret the closure of the Smethwick site.
They say they are working to find alternative roles for employees affected from the plant on Alpha Business Park site, in Bevan Way.
Union officials say the decision has been taken due to the age of the plant and its need for modernisation.
The poultry plant employed 630 people, of which 250 have taken voluntary redundancy and 290 have been redeployed.
The remaining 90 workers are still waiting to hear their fate. It is due to close on June 23.
The group employs around 1,500 people at plants in West Bromwich and Wolverhampton as well as Smethwick.
A spokesman for the company said: "It’s with much regret that we have had to close one of the original 2 Sisters sites, but we have done our very best to find as many alternative roles as possible for colleagues.
"We are currently working hard to explore all job opportunities for the remainder of colleagues over the next few weeks and are hopeful more roles will be found."
Julia Long, the Unite union's national officer for the food industry, today said the move was 'very disappointing' for the workforce.
"Through intensive negotiations we have managed to save about 250 jobs which will be taken up by other 2 Sisters sites in the West Midlands," she said.
"Unfortunately, this still means that some 300 workers face redundancy.
"However, given the company's business case that this site was ageing and needed drastic modernisation to conform environmentally, we believe that this was the only achievable outcome.
"Unite always has the welfare of its members as the top priority and we are continuing to support them in the days and weeks ahead."
Ward councillor Preet Gill said the closure was a 'big concern' and questions would be asked over what would become of the site.
She said: "It's a big concern, especially with job losses and what could happen with the future of the site.
"It's a loss because we're always trying to attract big investment.
"The council will support any of those worried or concerned about what's happened to them and support them with looking for new work.
Ninder Johal, Black Country LEP board member, said the closure was 'disappointing'.
He said: "This is clearly disappointing news. I'm hoping that the 90 people who could be made redundant will be able to find jobs within the 2 Sisters Group or with other firms.
"There's a skill deficit in the region. There's one thing we can be certain of, in this ever-changing climate with the advent of artificial intelligence and the increasing use of robots, manufacturing will witness further changes."
In March, more than 100 workers from the 2 Sisters Food Group protested outside Tesco in a row over employees’ rights.
WATCH: See how workers from 2 Sisters protested outside Tesco in West Bromwich
A demonstration was held by workers outside Tesco in West Bromwich’s New Square shopping centre after Unite’s acting national officer hit out at the management.
The union claimed that new management had ‘unpicked many years of established and stable industrial relations’ at the five Unite-recognised plants across the Midlands.
2 Sisters bosses responded stating that the allegations made against the firm, including claims that it used covert CCTV and audio recording equipment to spy on workers, were ‘untrue’ and ‘misleading’.
The Smethwick plant opened in 1996 and supplies retailers and other manufacturers with chicken portions. All of the work at the plant has been relocated to other UK sites.