Additive manufacturing of polymers is used for rapid prototyping and in specifc applications for the fabrication of fnal products. As the application range grows to the industrial sector, functional parts require better mechanical properties and tighter tolerance ranges. Short-fber reinforced polymers can handle higher stresses and signifcantly less deformation tan raw AM polymers, but their surface roughness and viscoelastic behavior are poorly understood. The authors perform the dynamical mechanical analysis, line, and surface roughness characterization of fused flament fabricated composites in this work. Mainly, Onyx, a short carbon-flled fber nylon thermoplastic composite, was used in three diferent build orientations: fat, on-edge, and upright. Then, the efect of build orientation on the viscoelastic and roughness properties is discussed. Results showed that despite using the same raw material, printing direction has a moderate impact on the viscoelastic behavior and a signifcant efect on the surface roughness of the part. For instance, a diference of 25 °C in the Tg was observed between the on-edge and upright build orientation, with the latter the highest. Also, the fat print orientation presented the lowest values in the z-roughness of all the three build orientations analyzed