In the current study, 3, 5 and 8 at% aluminum were added to Cantor alloy, and the subsequent effects on microstructure, recrystallization temperature, hardness and work-hardening rate were investigated. For this purpose, the alloy was prepared employing vacuum arc remelting method. After casting, homogeneous annealing and cold rolling, the samples were annealed at different temperatures of 400–1100 °C for 1 h. Results showed that the melting point decreased with increasing aluminum content, while recrystallization was delayed with an increase in the temperature. The recrystallization temperature of the Cantor alloy by adding of 3, 5 and 8 at% aluminum increased from 800 to 900, 1000, and 1100 °C, respectively. In the annealing process of the samples, it was found that the B2 precipitates formed and the hardness of the alloy increased significantly by 8 at% Al at 600 °C. Furthermore, addition of Al to a Cantor alloy also increased the lattice strain and consequently reduced the stacking fault energy. A new kind of nanotwinned materials called hierarchical nanotwinned have been developed and could be more important in strain-hardening capability. Therefore, the behavior of work-hardening rate of the alloy indicated the effect of twins on the deformation mechanism of the alloy. Finally, the presence of nanotwin and B2 precipitates was investigated by TEM.