This work describes a novel approach of three-dimensional (3D) printing to fabricate 3D porous models in one step, which we termed immersion precipitation 3D printing (ip3DP). Methods to impart porosity to 3D printed objects have been limited to date. The addition of sacrificial materials to printing materials, followed by their removal, are the established approaches, but such approaches require post-processing to impart porosity. Solvent-cast 3D printing (SC3DP)—direct 3D printing of polymer inks with in situ evaporation of solvents—has allowed fabrication of 3D porous structures with stringent requirement of rheological properties of the printing ink (e.g. high viscosity and high vapor pressure). In our approach, we printed polymeric inks directly in a bath of a nonsolvent and solidified them in situ via immersion precipitation. Spontaneous solidification via immersion precipitation generated porosity at micro-to-nano scales. The porosity of the 3D printed objects was readily controlled by the concentrations of polymers and additives, and the types of solvents. This work is the first demonstration of three-dimensionally controlled immersion precipitation based on digitally controlled depositions of materials. A wide selection of printable materials, and the ability to tailor their morphologies and properties, make ip3DP a versatile method of 3D printing.