In this study, the effect of Pb element addition varied between 0.2-0.4 wt.% on the microstructure and casting properties of AZ91 magnesium alloy were investigated. The microstructural results showed that as increasing Pb additions into the AZ91 alloy, the grains and the Mg17Al12 intermetallic phase becomes thinner. When examining the effect on casting properties; It was observed that the fluidity of AZ91 alloy increased as the increasing of Pb additions. In the hot tear tests two different mold systems were used. Hot tearing were observed in the longest section in the tests using" the mold same diameter, different lengths" and when the" the mold different diameter, same lengths" were used, hot tears were observed in all of the molds with diameters of 6, 8, 10 mm. Hot tearings were observed in 0.2 wt.% and 0.3 wt.% Pb additions, while hot tearing was not observed when this ratio increased to 0.4% for the 12 mm diameter test specimens. There was also not hot tearing were observed in any sample when the sample diameter was 16 mm.