Scour is a natural phenomenon caused by the removal of silt from alluvial beds caused by a stream's erosion, which happens around or next to moving water structures. Various studies have been conducted to understand better local scour events in order to construct hydraulic structures safely and economically. This paper investigated the use of a sill under the gate and its effect on the maximum scour depth downstream of a sluice gate. The experiments were performed at different relative sill heights (hs/Ls = without sill, 3.8, 8.0, 12.0, and 15.0%), and with various relative gate openings (a/Ls) of 13%, 18%, and 23%. The results revealed the effectiveness of the sill under the gate in decreasing the maximum scour depth. All sill heights reduced the maximum scour depth downstream of the sluice gate. The relative sill height of 8% gave the minimum value of the maximum relative scour depth for all relative gate openings. The results of this study can be used in the design considerations for gates and their protection.