This study provides a comprehensive analysis of the effects of incorporating low levels of cellulose nanofibrils (CNFs) into an acrylonitrile butadiene styrene (ABS) matrix on the properties of ABS composites. Five samples with varying CNF content (0.125%, 0.25%, 0.5%, and 1%) were prepared, alongside a pure ABS sample for comparison. The preparation involved mechanical blending, followed by extrusion and injection molding. Mechanical, thermal, water absorption, surface gloss, and microstructural properties of the composites were characterized. Tensile and three-point bending tests revealed that the addition of CNFs improved both stiffness and strength, with the highest tensile modulus observed in ABS/NC4 (1% CNFs) and the highest flexural strength in ABS/NC1 (0.125% CNFs). Impact resistance, evaluated through Charpy impact testing, showed enhancement up to 0.5% CNF content, beyond which a decline was observed due to increased particle quantity. Thermal properties exhibited negligible changes, with slight variations in glass transition and melting temperatures observed within a narrow range. SEM analysis confirmed a uniform distribution of CNFs, contributing to enhanced crack resistance, although higher CNF content led to increased void formation. Surface gloss measurements indicated smoother material surfaces with higher CNF content. The study concludes that integrating CNFs into ABS composites improves mechanical properties and impact resistance, necessitating careful consideration of CNF content for optimal performance. Further refinement could tailor ABS/CNF composites for specific applications.