The agency won the account after a four-way pitch and will work on a brief to develop brand awareness and increase passenger numbers over the next three years.
Brittany Ferries, which operates from ten ports linking the UK and Ireland to France and Spain, previously worked with Walker Agency on its integrated advertising and AMS on the media account.
Bray Leino, part of The Mission, will handle the business from its Bristol office. It will be overseen by Alistair Bryan, the managing director, and Jon Elsom, the executive creative director.
Richard Price, the head of marketing at Brittany Ferries, said: "Brittany Ferries has a track record of building long-term partnerships to deliver consistent and effective marketing campaigns and we look forward to working with Bray Leino to help us deliver some ambitious growth targets."Follow @Darbs73