Being a combustible material, timber has not benefited from recent advances in fire research and associated computational work. However, as the design of timber structures is moving from prescriptive to performance based, there is a need for the development of material models that can be used in numerical simulations to predict fire resistance. A model based on continuum mechanics is therefore presented for the determination of the load bearing capacity of multi-dowel timber connections under fire. The model applies the classical flow theory of plasticity. It takes into account the orthotropic elastic behavior, the plastic anisotropic hardening, the large plastic deformations, and the effect of heat. Qualitatively, the predicted results agree with the experimental ones. The model can be easily implemented as a subroutine in existing finite element software.