Starch has been blended with poly(butylene adipate-co-terephthalate) (PBAT) aiming to develop sustainable filaments for fused deposition modeling (FDM). Due to their distinguishable chemical nature, synthetic compatibilizers have been used in starch/PBAT-based blends, affecting their production cost. In this work, the feasibility of using non-purified starch and spent frying oil (SFO) recovered from potato washing slurries and potato frying residues, respectively, to enhance the extrudability and FDM capacity of starch/PBAT-based formulations was studied. The influence of SFO amount (1-3% wt. starch weight) on melt fluidity and moisture content of starch-based formulations was evaluated. For the most fluid starch/SFO-based material, the influence of PBAT concentration (15%, 30%, 45% wt.) on melt fluidity, microstructure, viscoelastic properties, extrudability, and FDM capacity was analyzed. Results revealed that SFO increased the melt fluidity of thermoplastic starch (TPS)-based granulates, while decreasing their moisture content. When mixed with PBAT and extruded, TPS/SFO-based formulations allowed to obtain filaments with homogenous microstructure and enhanced melt fluidity. Storage modulus of the TPS/SFO-based filaments increased by increasing the PBAT content, leading to a slight rise in the glass transition temperature. Even for the lowest PBAT amount studied (15%), the developed TPS/SFO/PBAT-based filaments were compatible with the FDM technology. Therefore, blending non-purified potato starch and SFO with PBAT allowed develop fluid and tough to traction biobased and thermoplastic filaments, facilitating their processability by FDM.