Multi-functional additive manufacturing is a promising route to achieving exciting new rapid prototyping and in-the-field manufacturing capabilities. Ideally, multi-functionality could be imparted to materials that can be used with existing additive manufacturing hardware with little-to-no modification of the hardware. However, because much of the additive manufacturing hardware currently available is highly sensitive to the properties of the input material, it is important to understand the relationship among the processing/development of the input material, its physical properties, and quality and properties of the additively manufactured part. To that end, this project explores the effects of processing conditions on the electrical properties and printability of nanofiller-modified fused deposition modeling (FDM) filament. Specifically, pulverized polylactic acid (PLA) is dry mixed with carbon nanofibers (CNFs) and extruded through a commercially available single-screw filament extruder. Filament resistivity and diameter are then statistically characterized as a function of extrusion temperature and number of extrusions. Printability is also quantitatively and qualitatively characterized using a commercial FDM printer. Insights developed through this work could be of considerable significance to next-generation additively manufactured piezoresistive-based sensors, actuators, and electrical components.