The effects of two distinct groove designs with differing groove volumes on the mechanical and metallurgical characteristics of 20 mm thick Hardox400 steel welded joints were investigated experimentally. The same number of weld passes (4 nos. each) were used to fabricate these welded joints (JV1, which corresponds to 45°, and JV2, which corresponds to 60°), which led to a variation in heat input. Optical microscopy measurements were used to conduct metallurgical analyses of the welded connections. The study’s findings show that of the several types of groove designs with different groove volumes employed for welding, the JV2 junction had the highest yield strength, ultimate tensile strength, and maximum joint efficiency. However, because of the increased groove capacity, the heat-affected zone’s overall breadth expands dramatically.