2 Sisters has been granted approval to build a 900sq m extension of the factory in Durranhill Industrial Estate.
This single storey building, an infill between two existing buildings, will house additional production space and storage, states the plans.
A new chill extension, measuring 195sq m, is also part of the expansion. This would be built onto the southern elevation of the current building.
Plans also include the installation of three new windows and two dock levellers.
The news comes as workers at the closure-hit Pinneys of Scotland factory are leaving their jobs ahead of its shutdown.
The workforce at Pinneys of Scotland, from Cumbria and the south of Scotland, were told they would lose their jobs after Young’s Seafood announced in April.
The fish firm had signed three contracts with M&S to supply the high street giant with chilled and frozen coated fish, natural salmon and white fish from 2018 to 2023.
It plans to move natural salmon production from Annan to Grimsby and exited deli and meals production.
The firm said this was no longer financially sustainable at Pinneys, resulting in the closure of the factory and the loss of 450 permanent jobs.
Efforts to secure employment and find a buyer for the site have proven unsuccessful.