The South-Pyrenean Tertiary Basin was an east-west trending foreland trough which developed from Early Eocene to Miocene times in a north-south trending compressive regime. A turbiditic series of Lower and Middle Eocene age (Hecho Group) enables us to define the typical features of the tectono-sedimentary evolution of the basin: (1) slope and shelf derived carbonate turbidites and megaturbidites bear witness to the seismic activity of the basin borders, (2) the southern basin border, evidenced by the onlap of the turbidites onto slope and shelf deposits, migrated progressively southwards in time and (3) the deformation pattern is characterized in the Meso-Cenozoic sediments by a complex thrust-fold system of thin-skinned tectonics style; its specific geometry and kinematics were influenced by the pre-deformation geometry (onlap). This thrust-fold system is related to south-directed basement nappes, and its front advanced progressively southwards in time. From this data, we infer an evolutionary model for this highly mobile basin: it was a flexural basin linked to the northward bending of the lithosphere in the foreland of a south-directed crustal accretionary prism; as the nappes advanced, the basin migrated progressively southwards, in the foreland direction. As for the actual basin evolution, many analogies with accretionary prism-trench systems of active margins exist.