The company is contacting all affected passengers
Brittany Ferries says its sailings from Ireland to France for Friday and Saturday are cancelled.
It says this is due to "adverse weather conditions".
Met Éireann have issued a number of weather warnings as Storm Brian heads for Irish shores.
Services from Roscoff to Cork on October 20th, and Cork to Roscoff on October 21st will not sail.
The company says it is contacting all passengers scheduled to travel to offer assistance.
Affected passengers can also contact the Brittany Ferries call centre at 00-353-21-427-7801.
The company has also apologises to all passengers for the inconvenience.