Abstract This note presents a damage model for fibre-composite materials based in the approach by Matzenmiller et al. [Matzenmiller, A., Lubliner, J., Taylor, R.L., 1995. A constitutive model for anisotropic damage in fiber-composites. Mech. Mater. 20, 125]. In this work, the model is developed in a three-dimensional context with modified formulation for the constitutive law and damage evolution. An orthotropic composite subjected to mixed failure modes is assumed in this development. Its formulation and implementation details are provided.