Abstract : A sediment wedge, about 20 m thick, has emplaced at the mouth of the River Seine during the Holocene transgression. Two main methodological approaches have been developed to determine the controlling factors of its construction and morphosedimentary evolution: (1) very high resolution seismic investigation coupled with vibro-coring for studing the pluri-millenial evolution; (2) historic bathymetric chart comparison to analyse the centennial to pluri-annual evolution during the last two centuries. The long term (Holocene) evolution is controlled on one hand by the rate of sea level rise, on the other hand by the position of the main fluvial incision. The tidal inlet system remains active all along the construction above the incision, whereas the adjacent areas, particularly in the South, have filled rapidly. During the last two centuries, the infill can be divided into 3 main stages: from 1834 to 1875, the mouth is a wide migrating channelized system; from 1875 to 1960: supratidal areas develop and lateral infill occurs; from 1960 to now-days: the infill is mainly up-to downstream and marked by the development and rapid seaward progression of two tidal longitudinal bars. The impact of natural factors on this recent evolution is hard to identify as management works during this period are major; they are assumed to be the controlling agents. However high frequency climatic cycles such as the NAO (North Atlantic Oscillation) seem to play a significant role in the morphodynamic behaviour of the tidal mouth during the most recent period, as since the 1980's no more major managements have been performed.