Transition criteria for crossflow instability are investigated in order to apply the γ-Reθ transition model to boundary layer flows with strong three-dimensionality. The criteria are evaluated by comparing their predictions with experimental results for the flowfields around a cylinder at various yaw angles, and the flowfields around a swept wing. It is found that the crossflow criterion proposed by Kohama et al. is a promising one because it can be evaluated by using only local flow variables. Transition prediction of a yawed cylinder has been performed by the γ-Reθ transition model with the proposed crossflow criterion. The production of eddy viscosity due to the present criteria was confirmed. A modification of the criterion was suggested to treat its dependency on flow conditions.