In this study, Q235 steel was welded by linear welding and oscillating welding using an IPG YLS-6000 fiber laser and oscillating welding head. The microstructures and mechanical properties of the two welded joints were compared and analyzed. Results show that laser beam oscillating welding can significantly increase the weld width from 1.34 mm to 1.60 mm when compared with linear welding; the microstructures of the two welded joints are lath martensite, lath bainite, and grain boundary ferrite; the complete austenitizing zones in heat-affected zones are made of ferrite and lath martensite, and the incomplete austenitizing zones consist of ferrite and pearlite with uneven grain sizes. The overall hardness of the oscillating welded joint is higher than that of the base metal. In addition, the tensile strength of the oscillating welded joint is 1.74 times that of the base metal, while the ductility and impact toughness of the joint are 66.7% and 90% that of the base metal, respectively. The oscillating welded joint has the same mechanical properties as the linear welded joint. Oscillating welding can effectively reduce the gap requirement associated with laser welding and has no adverse effects on the hardness, strength, and toughness of the welded joint.