Three‐dimensional printing (3DP) plays a significant role in developing custom analytical devices and miniaturized measuring systems. The printing materials, for example, polymer filaments, are often regarded only from the point of view of their mechanical properties to achieve the desirable geometry of a 3D‐printed item. Nevertheless, the modification of 3D printing materials to give them new features, such as luminescence, opens the way to the highest level of customization for various applications. In this work, glycol‐modified polyethylene terephthalate is mixed with luminescent complexes of Eu(III) to extrude the filaments suitable for fused deposition modeling of a cuvette for chemical analysis. This cuvette is the main part of a miniature spectrophotometer, being a light source and a sample chamber itself. As a proof of concept, the developed spectrophotometer is applied for quantitative digital image‐based analysis of inorganic and organic substances.