The company employs about 470 staff at its site in Strawberry Hill
Pharmaceutical giant Bayer is moving its UK headquarters about 20 miles.
The company employs about 470 staff at its site in Strawberry Hill, Newbury, where it has been based since 1983, but wants to move to modern premises in Green Park, Reading.
A spokesman for the company said it hoped to relocate all its employees. The moving date has not been announced.
Richard Benyon, MP for Newbury, said the town was going to lose an "old friend".
Simon Greenstreet from Bayer said the decision came about because the current building was too large, and because the lease expires in 2018.
It also had a leaking roof and needed an "entire refurbishment", he said.
The company looked at more than 30 potential sites, including nine in Newbury.
Mr Benyon said: "Bayer's been part of Newbury life for 30 years.
"We worked so hard with Bayer to try and find a site… I've been frustrated, they've no doubt been frustrated."
But he said Newbury was booming town and would continue to thrive.
Gordon Lundie, leader of West Berkshire Council, said the move would have a negative impact on the town's businesses.
"We've got to think about how we manage to blunt the impact of that [and] work out how we try and support the local economy," he said.
But he said it was "great" that the company was "reinvesting into the royal county".
