Asthenognathus atlanticus Monod, 1932, has been reported for the first time from the eastern part of the Bay of Seine (eastern English Channel). A total of 30 specimens were collected between the years 2008 and 2011, along the Normandy coast from Ouistreham to Antifer, mainly on mud and muddy sand habitats, between 10 and 25 m depth. The distribution range of A. atlanticus has been previously known to cover eastern Atlantic coasts from Angola to the western English Channel, where it reached its northern limits. It is also present in the western part of the Mediterranean Sea. The changes in the sediment composition of the eastern Bay of Seine have probably led to the development of a potentially favorable habitat for this species. However, the data collected have not yet been sufficient to ascertain the origin, and the method of introduction of the eastern English Channel specimens. In the discussion, we ponder if they might have originated from the western English Channel populations, and was transported as larvae in the eastern English Channel; they could have originated from a more distant population, and have been brought to the eastern English Channel through human activities. Each hypothesis is possible in theory.