Weekly flights will start on June 29 and run throughout the peak summer period.
The carrier will operate a Saturday service from Dublin to Brest with schedules designed to benefit Dublin based leisure travellers looking to visit the Brittany region.
Flights will depart Dublin Airport at 13:05, arriving at to Brest Bretagne Airport at 15.30.
The return flight will leave Brest at 16.15, arriving in Dublin at 16.40.
The CityJet network covers 22 European destinations across Belgium, France, Germany, Ireland, Italy, Luxembourg, the Netherlands and the UK.
The Dublin–Brest route will be operated by an Avro RJ85 jet with a seating capacity of 95.
Christine Ourmières, CEO of CityJet, said: “Brest is a popular summer destination, so we are delighted to be able to offer Dublin based passengers’ direct access to the heart of this stunning region – one of France’s best-loved destinations.
“Our service from Dublin offers a convenient schedule for families enjoying longer summer holidays during the school break period or those visiting their second home in Brittany.”