Several studies on barred beaches in settings with mesotidal to macrotidal regimes have focused on crossshore and alongshore bar mobility. However, the role of coastal defense structures (breakwaters, groins, seawalls) on bar-trough systems morphodynamics have received more much less attention. The main aim of this paper is to highlight the contrasting behavior of a natural and protected barred beach under several hydrodynamics conditions. This paper presents detailed hydrodynamic and morphological data from a field experiment undertaken in Matalascañas beach, a mesotidal protected vs natural barred beach in the Southern Spanish coast. The non-protected beach shows a less pronounced bar-trough system than the protected zone. Under low energy conditions, onshore bar migration rate in the protected area was more important than the non-protected area. This migration was associated with an onshore sediment transport, resulting from the erosion of the bar’s seaward slope. In the same moment, a clear longshore bar migration was observed in the non-protected zone. During few energetic tides, the protected and non-protected zones show a flattening bars processes. The findings of the present study suggest that cross-shore vs longshore bar mobility may even be mitigated by the presence of the groins, which favor onshore than longshore bar migration. Key words: Dissipative beach, bar dynamics, groins, Matalascañas, Huelva.