This work investigates the preparation of silicon carbide ceramics (C/Si/SiC ceramics) from extruded thermoset-based wood polymer composites (WPC). The extruded WPC green bodies are carbonised forming open porous carbon templates (C-templates). These C-templates are converted by liquid silicon infiltration into bio-based C/Si/SiC ceramics. The materials over the whole process chain (WPC → C-template → C/Si/SiC ceramic) are characterised by density and porosity measurements, mechanical testing, light optical microscopy, scanning electron microscopy and X-ray computed tomography. Extruded thermoset-based WPC can successfully be used for the production of C/Si/SiC ceramics. Different 3D geometries have been processed by profile extrusion. The main impact factor on the quality of the porous C-templates and subsequent C/Si/SiC ceramics is the distribution of the constituents as well as the density distribution in the green bodies. Variations in the composition of WPC, especially the thermoplastic content, allow adjusting the porosity of the C-templates formed after pyrolysis. From optimised WPC green bodies, C-templates without distortion (isotropic shrinkage) and homogeneous pore distribution and subsequent C/Si/SiC ceramics with SiC contents up to 90 vol% (95 wt%) could be produced.