The present study demonstrates the feasibility of stereolithographic 3D printing of composite objects based on acrylic photo-curable formulations, containing in situ generated silver nanoparticles (AgNPs). The starting resin was prepared on the bases of commercially available acrylic resins and photo-initiators with the presence of different silver salts (silver acetate, silver acrylate and silver methacrylate), soluble in the initial liquid formulation. Contrary to the simple mixing of preformed solid nanoparticles to liquid photo-curable resins, the presence of a soluble AgNPs precursor was crucial in order to maintain the viscosity of the liquid system to values low enough to be compatible with the stereolithographic printing process. During the 3D printing process, the laser radiation of a commercial stereolithography printer (Form2, Formlabs Inc.) was used to both selectively polymerize, layer by layer, the acrylic resin and to activate the reduction of the soluble silver salt to solid AgNPs. The morphology of the obtained nanocomposites was investigated by means of electron transmission microscopy, demonstrating the presence of well dispersed and distributed AgNPs within the polymer matrix. The presence of the filler caused a significant increase in the physical and mechanical properties of the samples that become significantly stiffer and stronger than the pristine matrix.