In this study, effects of solidification rate and 0.2, 0.5 and 1.0 wt-% Sb additions on the microstructure and mechanical properties of AM60 magnesium alloy were investigated. AM60 and AM60+xSb magnesium alloys were cast in a step-like mould with three different cooling rates. As cast microstructures of the different steps were examined with optical microscope, XRD, SEM and EDS. The results showed that grain structure became finer as the cooling rate increased which resulted in enhancement in the mechanical properties. Tensile and yield strengths reached the peak values as Sb content was 0.2% which yielded 30 and 28% higher strengths respectively as compared to the base AM60 alloy.