<p>Additive manufacturing, particularly laser additive manufacturing (LAM), has revolutionized the field of materials engineering by enabling the precise fabrication of complex geometries with bespoke properties. This technology uses laser energy to locally melt source metal material in the form of powder or wire layer-by-layer to create three-dimensional objects. The versatility of LAM provides a unique opportunity to utilize a wide range of metallic alloys and composite materials, allowing advancements in industries such as aerospace, automotive, and biomedical engineering. Despite the remarkable potential of LAM, a critical challenge facing its adoption is the potential variation in alloy compositions during the additive manufacturing process. These variations can arise from factors such as selective evaporation of alloying elements, oxidation, or fluctuations in the thermodynamic conditions of the melting-solidification cycle. Addressing these issues requires a nuanced understanding of the in-line chemical and physical transformations that occur. Spectroscopic approaches provide real-time monitoring capabilities to detect and quantify compositional changes, offering a pathway to better control and stabilization of the LAM process. We have developed an optical emission spectroscopy system for in-line composition monitoring during the laser metal deposition process. The system is based on a high-resolution optical spectroscopy sensor and allows the in-line collection of unique spectral features intrinsic to the materials used. Using intelligent data analysis and machine learning methods, the system can tailor the additive process parameters to achieve the desired material composition, as well as optimal biochemical and biomechanical compatibility characteristics. The capabilities of the developed spectroscopic system have been demonstrated in the additive manufacturing of superelastic titanium–nickelide and magnesium alloys and surface structures suitable for medical use.</p>