Philippe Lesaulnier, 48, died when his fishing boat was hit by the 800-gt Condor Vitesse(built 1998) in 2011.
First officer Yves Tournon was given a 12-month suspended sentence for manslaughter in 2013.
This was overturned due to uncertainties over whether the ferry's radar was functioning properly, the BBC reported.
Captain Paul Le Romancer had his 18-month suspended sentence upheld, however.
Delphine Lesaulnier, the victim's widow, said she was "disheartened and deeply disappointed".
