In this paper, the analytical stress intensity factor and J integral solutions for welds in lap-shear specimens of two dissimilar sheets based on the beam bending theory are first reviewed. The solutions are then presented in the normalized forms. Next, two-dimensional finite element analyses were selectively conducted to validate the analytical solutions based on the beam bending theory. The interface crack parameters, the stress intensity factor solutions, and the J integral solutions for welds in lap-shear specimens of different combinations of steel, aluminum, and magnesium, and the combination of aluminum and copper sheets of different thickness ratios are then presented for convenient fracture and fatigue analyses. The transition thickness ratios for critical crack locations for different combinations of dissimilar materials are then determined from the analytical solutions. The transition weld widths for applicable ranges of the weld widths for the analytical solutions based on the beam bending theory are also presented. Finally, fracture and fatigue behaviors of dissimilar magnesium/steel ultrasonic welds, dissimilar aluminum/copper laser welds, and similar steel laser welds in lap-shear specimens are examined and demonstrate the usefulness of the stress intensity factor solutions presented in this paper.