Self-hardening aluminium alloys represent a new and interesting group of aluminium alloys. They have the advantage that they do not need to be heat treated, which is an important advantage that contributes to a significant reduction in production costs of some components and in the amount of energy used. The present paper deals with the possibility to replace the most used heat treatable AlSi7Mg0.3 cast alloys with a self-hardened AlZn10Si8Mg cast alloy. In this study, microstructural characterization of tensile and fatigue-tested samples has been performed to reveal if this replacement is possible. The results of fatigue tests show that AlSi7Mg0.3 alloy after T6 heat treatment and self-hardened AlZn10Si8Mg has comparable values of fatigue properties. The self-hardening alloy has slightly lower strength, ductility, and hardness.