Statistics for The concept of rubble mound breakwater and submerged reef breakwaters, operating together as a single unit, is called the tandem breakwater. The effect of the submerged reef breakwater on the stability of non-overtopping rubble mound breakwater on its leeside was investigated in the present study, The tandem breakwater was tested for two spacings between the breakwaters, ie,for 1 m and 2,5 m. For each of the spacing, the effect of water depth, wave-period and wave height on the stability of tandem breakwater was studied. In the present study, the damage level of tandem breakwater for a relative spacing varying from 2.22 to 7.14 was 10% to 40% less compared to that of a single breakwater designed to meet the same operating criteria.