The failure mechanism in staple yarns is strongly influenced by yarn structure. Manufacturing methods impose certain constraints on the disposition and distribution of fibers in the yarn cross section. This paper investigates the failure mechanism in ring, rotor, air-jet, and vortex yarns. The yarns are subjected to uniaxial loading on a tensile tester, and images of the yarns before and after breaking are recorded. Image analysis of the failure regions yields some interesting features and reveals typical mechanisms occurring in different yarn structures. The failure mechanism in each yarn type is discussed in terms of some basic parameters characteristic of the structure.