Facet-dependent photocatalytic properties are intrinsic characteristics of several inorganic semiconductors. Herein, faceted crystal engineering and 3D-printing technology have been combined for the fabrication of the first organic–inorganic 3D-printed visible-light photocatalyst prototypes. As a proof-of-concept, two facet crystal nanoarchitectonics have been devised by in situ synthesizing Ag₃PO₄ nanoarchitectures with tunable─amorphous and faceted─shapes upon 3D-printed graphene/polylactic acid (G/PLA) nanocomposite scaffolds through a green wet-chemistry approach. The facet-dependent photoactivity performance of the resulting 3D-printed photocatalysts under visible light irradiation has been explored toward (i) the photodegradation of environmental pollutants (i.e., rhodamine B) and (ii) the indirect photoelectrochemical oxygen evolution from water splitting. Overall, the 3D-printed G/PLA carrying facet-Ag₃PO₄ nanoarchitectures has displayed enhanced photocatalytic and photoelectrochemical activity when compared to its amorphous-Ag₃PO₄ counterparts. Accordingly, the integration of inorganic semiconductors across low-cost 3D-printed G/PLA scaffolds under crystallization control represents a potential nanotechnological strategy toward the next generation of highly efficient organic–inorganic 3D-printed solar-light-driven photocatalysts, which might be mass-produced in a sustainable way, anywhere at any time.