Arch-shaped members are used in many reinforced concrete structures such as tunnels, bridges, silos, or offshore constructions. They are generally designed to carry significant axial forces, and, in most cases, are not provided with transverse reinforcement. Depending on the applied actions, however, bending moments and shear forces may also develop. This can potentially lead to spalling failures of the concrete cover or to shear failures where the strength may be reduced in comparison with straight members. Such reduction is due to the curvature of the element and to the corresponding deviation forces originated by the compression and tension chords. In spite of the significance of the topic, little research has been performed. In this paper, the authors summarize the results of a comprehensive investigation comprising an experimental part on nine arch-shaped specimens with thickness equal to 400 mm (15.7 in.). On the basis of these results, the basic failure mechanisms and shear-transfer actions are identified. By using the principles of the critical shear crack theory for assessment of the shear strength, a design approach for such members is presented that accounts for the various mechanical and geometrical parameters. The approach provides consistent and accurate predictions when compared with the tests presented in the paper.