We report on the development of a miniaturized device for operando X-ray diffraction during laser 3D printing. The printing chamber has a size of only 130 × 135 × 34 mm³ and is optimized to be installed at synchrotron beamlines. We describe the design considerations, details on the setup and the implementation at two different beamlines of the Swiss Light Source. Its capabilities are demonstrated by ex situ printing of complex shapes and operando X-ray diffraction experiments using Ti-6Al-4V powder. It is shown that the beamline characteristics have an important influence on the X-ray footprints of the microstructural evolution during 3D printing. From the intensity of the diffraction peaks, the evolution of the different phases can be followed during printing. Furthermore, the diffuse scattering signal provides information on the precise location of the laser beam on the sample and the scanning head settling time.