The development of lightweight composite structures to satisfy the demands of the aerospace, medical, and automotive sectors has resulted in an increasing demand for 3D-printed parts. Fused filament fabrication is a popular and cost-effective way to produce complex and flexible prototypes and parts without wasting materials. However, the qualities, i.e., strength and surface roughness, of 3D-printed parts are still inferior to those produced through conventional manufacturing processes. Thus, the primary objective is to increase the surface quality of 3D-printed composite parts. To achieve this goal, a composite feedstock filament was developed using cenosphere and polyethylene terephthalate glycol thermoplastic material. Furthermore, the influence of process parameters such as extrusion temperature (A), layer height (B), and printing speed (C) was examined to improve the surface characteristics of FFF parts. The study found that printing temperatures followed by printing speed are the most significant factors in improving surface characteristics. The optimized settings of 250 °C printing temperature, 0.20 mm layer height, and 50 mm/s printing speed were identified as the best to produce parts with better surface quality.