Correct description of the ductile failure phenomenon for hcp metallic materials is still an open problem as opposed to the well-grounded studies available for phenomenological material description or more recent crystal plasticity frameworks for fcc metals. Hcp metals, especially in the form of single crystals and polycrystals with a strong texture, are highly anisotropic in terms of the plastic properties and suffer from low ductility and fracture toughness. As a step forward towards constructing the predictive model of ductile failure for such crystalline solids, the initial yield surface of the porous hcp single crystal deforming by slip and twinning is formulated using micromechanical elastic-viscoplastic model. The result is obtained by applying multiscale micromechanical framework. The use is made of own existing proposals of the crystal plasticity model of respective non-porous medium and the micro-macro transition schemes based on the sequential/additive linearization method. The proposal is validated with respect to the full field FE analyses on unit cells subjected to the multi-point constraint boundary conditions enabling to control triaxiality and Lode parameter for overall Cauchy stress. Using the proposed yield surface the analysis of multiple factors influencing material yielding will be performed, including overall loading scheme, local crystal orientation, initial porosity, and in particular twinning activity. The research is partially supported by the project No. 2021/41/B/ST8/03345 of the National Science Centre, Poland.