Mixed-mode fracture of concrete is encountered frequently in design of concrete structures. To accurately analyzed and design a concrete structure, it is essential to understand the failure mechanisms of concrete under mixed-mode types of loading. A model, which was originally proposed for mode I failure of concrete, is extended to characterized mixed-mode crack propagation. Crack initiation angles, final failure path, and crack instability of concrete specimens/structures are discussed. A series of mixed-mode notched beam tests were performed to verify the proposed model. The theoretical predictions were found to be in good agreement with the experimental results.