In this work, a cast alloy of Al–Zn–Mg was developed from aluminium from recycled beverage cans and zinc scraps from battery and the influence of age-hardening heat treatment of the alloy on mechanical properties and reliability analysis on the tensile strength was investigated. The cast Al–Zn–Mg alloy was subjected to age-hardening heat treatment at different times. The aluminium, cast alloy and age-hardened alloy were characterized using XRF, XRD and TEM. The mechanical properties were investigated using a hardness test, impact strength test and percentage elongation. Also, the tensile strength data were subjected to a reliability analysis using Weibull probability distribution. From the results, it shows that 24 h ageing time is enough to have optimum mechanical properties due to an increase in size of the stable MgZn2s phase particles. The reliability analysis shows that the alloy aged at 24 h has tensile strength value (229.72 MPa) in the range reported for Al–Zn–Mg alloy’s temper designations.