The Hollow Triangle Breakwaters (HTBs) is widely constructed in the Vietnamese Mekong Delta (VMD) due to severe coastal erosion in recent years. This study aims at investigating the hydrodynamic performance, wave actions on the HTBs. Three-dimensional numerical modelling using modern MIKE 3 wave flexible mesh (FM) was successfully built for the optimal porosity cases (P1 = 22.5%; P2 = 11.8%) to explore the relationships of these hydrodynamic behaviors and wave interaction with the HTBs. This study showed results present of flow pattern, velocity fields, turbulent kinetic energy, vertical eddy viscosity and non-hydrostatic pressure in the HTBs. This can explain the vortex and eddy formations that cause the erosion at the front toe of the breakwater and the negative non-hydrostatic pressure inside the breakwater due to the effect of the baroclinic in the oscillation. These insights highlighted the importance of the numerical model which provided a greater understanding of the impact of the waves than the physical model. The HTBs provide an effective alternative at reducing the impact of waves while also allowing the exchange of sediment and facilitating aquatic species to thrive in the coast side construction in the VMD.