Summary: This paper investigates the directional stability of crack propagation in adhesively bonded joints. First, an analytical model analyzing the energy balance during the crack propagation in double cantilever beam specimens is presented, and the directional stability of cracks is predicted. The results are consistent with the predictions made by N. A. Fleck, J. W. Hutchinson and Z. Suo [Int. J. Solids Struct. 27, No. 13, 1683–1703 (1991)] using a stress analysis approach, and also are consistent with experimental observations. Similar to the situation in homogeneous solids, cracks in adhesively bonded joints also tend to be directionally unstable when the T-stress is positive (tensile) whereas tend to be directionally stable when the T-stress is negative (compressive). Both interface mechanics and the finite element method are then employed to analyze the stress state at the crack tip and to predict crack trajectories. Through extending the criteria for direction of crack propagation to bi-material systems, the trajectory for directionally unstable cracks is simulated. The simulation result accurately reflects the alternating nature of directionally unstable cracks in adhesive bonds such as the characteristic length and the overall shape.