A hemp-based composite filament (CF) for a fused filament fabrication (FFF) process was developed. The designed filament is based on hemp particles obtained from stack used for cannabidiol (CBD) production and PLA, a bio-based, biodegradable, recyclable plastic. The rheological properties of virgin PLA grains, commercial PLA, and hemp-PLA filaments were analyzed. Then, hemp powder was produced and separated according to particle sizes (75-150 µm and 150-300 µm). The hemp ratio used was 5% and 10% by weight. Next, filaments were extruded from a mixture of virgin PLA grains and hemp powder. Mechanical characteristics of standard specimens were determined. Also, the shape and size of hemp particles were observed. The extrusion temperature was the most prominent parameter. Created 3D-printed parts were more ductile. Moreover, the developed filaments showed lower viscosity that was inversely proportional to the size of the hemp particles and directly proportional to the hemp ratio particles in the composites. The effect of particle size was a more influential factor on viscosity than the hemp ratio in the composite. The ultimate tensile strength (UTS) of the newly designed filaments was lower but the elongation before failure was higher when compared to commercial filaments.