The cooling slope casting process has gained significant importance for the manufacturing of semisolid feedstock aluminum alloys, which find applications in the automotive and aerospace industries. The effect of the pouring temperatures on the microstructure of A356 aluminum alloy via semisolid casting using the slope cooling plate has been investigated. The prepared alloy that becomes semisolid at the end of the cooling slope plate is consequently poured into a sand mold. Without using the slope cooling plate, the α-Al phases became coarse dendritic structure with an average length of about 287.5 μm. In case of using the slope cooling plate at the optimum pouring temperature of 640°C, The α-Al phase developed a fine globular structure with the average grain size of about 72.6 μm. The tensile properties of the investigated A356 alloy were improved by the application of semisolid casting at the optimum pouring temperature of 640°C. The ultimate tensile strength and the elongation of the investigated alloy significantly increased from 102 MPa and 1.175% without semisolid casting to 113 MPa and 3.6 % with semisolid casting at the optimum pouring temperature of 640°C, respectively then gradually decreased with further increasing the pouring temperature. The fracture mechanism has been also investigated.