In general, micromilled mould inserts made of steel, aluminum or brass are used today for ceramic injection moulding (CIM) processes. However, tool making via mechanical subtractive manufacturing processes as micromilling is time- and cost-effective and the use of 3D printed mould inserts becomes an attractive alternative to metal mould inserts. In this paper, we report about the use of 3D printed mould inserts for CIM of alumina microreactor parts. It was observed that mould inserts printed using the Polyjet technology were very well suited for functional prototyping via CIM. The mould inserts surface was found without visible thermally introduced damage after twenty CIM process cycles. In contrast to the high quality of mould inserts printed using the PolyJet technology, mould inserts made via fused deposition modeling (FDM) technology revealed as not applicable for the purpose of this study. The mould inserts manufactured using FDM-printer exhibit significantly higher surface roughness, larger longitudinal deflection and manufacturing-related undercuts along the edges of the 3D printed microstructure.