Fused deposition modeling (FDM) is one of the most common additive manufacturing processes (commonly referred to as 3D printing) that uses a thermoplastic filament as feedstock for building three-dimensional objects. Polylactic acid (PLA) is an attractive and popular thermoplastic filament material; it is nontoxic, produced from renewable resources, and it is biodegradable. However, PLA has a relatively low strength and ductility. In this study, we produced PLA-nanocomposite filaments with up to 2.5 weight percent silver nanoparticle additives for FDM printing of objects with improved mechanical properties. PLA, silver nanoparticles, and a dispersant were mixed in chloroform and dried into a disc. The disc was granulated and extruded to produce a 1.75 mm filament. Transmission electron microscopy (TEM) of microtome-prepared filament cross-sections showed a uniform dispersion of nanoparticle additives throughout the polymer matrix. Differential scanning calorimetry (DSC) showed no significant change in the glass transition temperature or melting point of the filament at the additive loadings investigated. FDM was used to print tensile test specimens with the nanocomposite filament. Compared to pure PLA, the test specimens exhibited up to an 81% increase in ultimate tensile strength, a 93% increase of the elastic modulus, and a 33% increase in ductility.