Additive manufacturing technologies are characterized by complex process interrelations. Consequently, specifically adapted alloys are required to enable a robust building process. In particular, laser beam melting (LBM) is increasingly used for the fabrication of sophisticated functional parts for various applications in numerous industrial sectors, such as automotive and aerospace. However, process stability and repeatability are major challenges for industrializing LBM. This paper presents a comprehensive investigation of the influence of AlSi10Mg additives in a 316L stainless steel powder during LBM. A two-stage experimental approach was applied, during which the temperature field around the molten track and the number of spatters during the LBM process were determined by means of high-speed thermographic imaging. Furthermore, the microstructure of the additively manufactured specimens, the modified 316L stainless steel powder, and the respective raw materials was characterized by scanning electron microscopy. The experimental study described in this paper aimed to obtain correlations between the additive content (input), the temperature field of the molten track, and the microstructure (outputs). It was found that the cooling rate decreases with a higher amount of AlSi10Mg in the powder. Furthermore, the microstructure analysis demonstrated an increasing formation of the body-centered cubic phase with a higher fraction of AlSi10Mg. The conclusion is that additives in the powder considerably affect important key characteristics of the LBM process.