<p>Polymer composite filaments have the potential to expand the applications of Fused Deposition Modelling, a 3D printing process. The scarcity of functional filaments has fueled the development of composite filaments for usage in 3D-printed objects beyond the typical household application. To provide functional qualities and build a polymer composite, increased mass loading of the filler material is desirable to overcome the inherent features of the polymer. This study reports the fabrication technique of a molybdenum trioxide (MoO₃)-reinforced Nylon 12 composite. MoO₃ is an extensively used electronics material for semiconductor and optoelectronics applications, whereas Nylon 12 is a thermoplastic polymer with superior mechanical and thermal properties. MoO₃ of three different compositions (20, 30 and 50%) are reinforced with Nylon 12 to fabricate functional filament. XRD and FTIR analysis revealed the presence of MoO₃ within the composite filament. The FE-SEM analysis unveiled the uniform distribution of fillers throughout the polymer matrix and a defect-free surface of the filament. Further mechanical and thermal analysis of the fabricated filaments portrays excellent stability of the polymer composite despite the very high loading of the ceramic fillers with the polymer. This work paves the way for the quick and cost-effective development of strong and functional feedstock for 3D printing.</p> Graphical abstract <p></p>