This study investigated the applicability of low transformation temperature (LTT) welding consumables to improve fatigue strength against weld root failure. Transverse attachment joints formed by single-sided welding were fabricated using an LTT welding consumable and conventional welding consumable. Fatigue tests with out-of-plane bending loads revealed that higher fatigue strength and fatigue limit can be achieved in the joint with an LTT consumable compared with a conventional one. In addition, residual stresses around the weld bead were clarified by X-ray diffraction measurements and finite element analyses. The results indicated that the LTT consumable can reduce tensile residual stress around the weld and also introduce compressive residual stress to the weld root.