In this study, the effects of the cold chamber die casting parameters on high-speed drilling machinability of AZ91 Magnesium alloys were experimentally investigated. The influence of different casting parameters (casting temperature, molding pressure, and gate speed) on microstructure, mechanical properties and machinability characteristics (thrust force, tool wear, built-up edge, built-up layer formation, surface topography, chip morphology, and burr formation) were examined. The experimental results showed that the grain size of the conventional casting sample was around 50 microns, while in other cold chamber die casting tests, it varied depending on temperature, pressure, and gate speed. It was observed that the tensile strength values ​​of the samples produced with 1000 bar mold pressure were higher than those of other samples. In the formation of thrust force, the feed rate is more effective than the cutting speed. The least tool wear occurred in the drilling of the As-cast sample, while the highest tool wear occurred in the drilling of the sample which was produced with low pressure and low gate speed combination. As a result of the drilling tests, depending on casting and cutting parameters, three different types of chips were formed: fan, spiral cone, and long ribbon type. Furthermore, uniform and transient burrs in different sizes were observed.