Quasicrystals (QC) are a new class of materials besides crystals and amorphous solids and have aroused much attention of researchers since they were discovered. This paper presents a generalized fracture theory including the J-integral and crack closure integrals, relations between J 1 , J 2 and the stress intensity factors as well as the implementation of the near-tip stress and displacement solutions of 1D QC. Different crack deflection criteria, i.e. the J-integral and maximum circumferential stress criteria are investigated for mixed-mode loading conditions accounting for phononphason coupling. One focus is on the influence of phason stress intensity factors on crack deflection angles. Keywords quasicrystal • crack deflection • mixed-mode loading • fracture quantities • J-integral