Abstract: The effects of TiN on the microstructure and tensile properties of as-cast and extruded AZ61 magnesium alloy were studied by adding TiN with a mass fraction of 0.5% to the AZ61 magnesium alloy. The results show that after adding TiN, TiN particles appeared at the grain boundaries of the as-cast and extruded AZ61 magnesium alloy, and TiN did not undergo a chemical reaction with other elements. After adding TiN, the grain size of the as-cast alloy decreased from 243.2 µm to 90.2 µm, and that of the extruded alloy decreased from 8.1 µm to 5.1 µm. After adding TiN, the content of the second phase in the alloy increased significantly, the dynamic recrystallization behavior of the grains during the extrusion was inhibited, and incomplete dynamic recrystallization grains appeared in the microstructure. After adding TiN, the tensile strength, percentage elongation after fracture, and yield strength of the as-cast alloy decrease by 38.3%, 31.3%, 30.0%, and those of the extruded alloy decrease by 3.3%, 3.7%, 28.3%, respectively. The decrease in tensile properties was related to the segregation of the hard TiN phase at the grain boundaries, the generation of twins, the decrease in the Schmid factor, and the enhancement of the texture.