The turkey firm was sold to the food tycoon Ranjit Boparan on Tuesday.
There had been fears that the new owners would not take on the existing workers' pension scheme.
But Unite regional officer Steve Harley said: "We had productive talks and we were given guarantees that all current agreements will be honoured."
Unite said it understood that the Bernard Matthews final salary pension scheme was closed in 2004 and that its members presently have an alternative pension scheme which is unaffected the takeover.
The Boparan Private Office, the "chicken king" Mr Boparan's private investment, confirmed that the current pension arrangements with Bernard Matthews would continue under the new ownership.
Mr Harley met with representatives from Boparan at the Great Witchingham headquarters.
He said: "It was made clear that the new owner wishes to restore Bernard Matthews to its former position as a highly profitable business.
"This would be achieved by greater investment in the business, cost savings and utilising the present spare capacity at Bernard Matthews to process chicken and not just turkeys."
A union has welcomed reassurances from the new owner of Bernard Matthews over job security and pensions.