Marine is to step up production at its processing plant in Rosyth after being picked by Sainsbury's to supply fresh and smoked salmon.
It will take over Young's Seafood's contract with Sainsbury's in November.
Norwegian-owned Marine said it would increase its Rosyth workforce from 90 to about 350 over the next year.
Until now, the Rosyth plant, which opened in 2014, has focused on products under the Marine Harvest brand - Harbour Salmon Co.
The Sainsbury's deal will see volumes at the plant increase five-fold.
Fears have been expressed for jobs at Young's seafood factory in Fraserburgh, Aberdeenshire, after its parent company lost out in the tender.
In a statement, Sainsbury's said: "We have been carrying out a thorough review of our Scottish salmon suppliers to ensure we can offer our customers the best products possible.
"As a result of the supplier tender, we have given advance notice to Young's Seafood that they will no longer pack and process salmon products for us.
"Marine Harvest, our Scottish farmed salmon supplier, will take this business on which will be carried out at its new factory in Rosyth, Scotland.
"However Young's will continue to supply us with fish, including cod and haddock."
Andy Stapley, managing director of Marine Harvest Consumer Products, said: "This is excellent news for the company as well as for Rosyth and will mean significant expansion for the plant and more local jobs for the area.
"This latest contract builds on the strong relationship Marine Harvest has established with Sainsbury's over many years and is part of the company's strategy to manage the entire food production process from farm to fork."
Salmon supplier Marine Harvest is set to create 260 new jobs in Fife after picking up a major supermarket contract from a rival firm in a tender.