Due to the demand for high welding speed processes, the stability and mechanisms of such techniques have to be investigated and improved. Especially by combining laser and arc processes, interactions are used to increase process stability as well as welding speed. For this, a coaxial laser-plasma hybrid welding process for flux less joining of aluminum was developed. In this paper, the interactions between the laser and the plasma arc within this process are reported. The dominant mechanisms of interaction between laser and plasma arc are identified by varying main parameters like laser power, plasma current, and plasma polarity. This knowledge is needed to understand the process and to guarantee a stable and safe joining.