This work outlines the design, simulation, and fabrication of a millimeter-wave (mm-wave) frequency selective surface (FSS) integrated directly onto a 3D-printed die encapsulation. The cross-shaped slot FSS is designed to function as a bandpass filter centered at 77 GHz for on-package tunability. Stereolithography (SLA) 3D printing is used to fabricate encapsulations for silicon dies attached to a metallic QFN leadframe. Surface profilometry is used to assess the roughness of the SLA-printed surfaces, yielding roughness 25× lower than standard fused deposition modeling (FDM) 3D printing techniques. Finally, inkjet printing is used in a post-process fashion to fabricate the package-integrated FSS directly onto a 3D-printed die encapsulation as a proof-of-concept demonstration.