This paper aims to investigate the effect of different weld groove configurations on the residual stresses dispersed in 40 mm thick multipass high strength low alloy (HSLA) steel butt-welds. Two welded joints having double-V type groove geometry were prepared, one of which had an equal double-V groove, and the other had an unequal double-V groove appearance. The locked-in residual stresses present in the weld zone and heat-affected zone (HAZ) were evaluated using both computational and experimental approaches. Furthermore, the effect of restrained condition on the trend of residual stresses of the equal double-V groove weld was analyzed using computational modeling technique with varying weld pass sequence. Lastly, a feasibility study was conducted on the implementation of mechanical tensioning technique to mitigate the weld-induced residual stresses in thick multipass butt-welded joints. The findings show that using an unequal-V groove joint can effectively reduce residual stress levels in the bottom half of the weld. A restrained welding condition with a single directional weld pass sequence can adversely impact the intensity of residual stresses across the weldment. The transverse residual stress levels can be reduced in the weld zone and its vicinity by an amount equal to the corresponding applied mechanical lateral tensioning load.