The Hardening by cold work is capable of increasing the mechanical strength of non-ferrous metals. The combination of alloying elements in solid solution and cold working is extremely effective in achieving greater strength for aluminium alloys. However, some alloys may be susceptible to stress corrosion and are notoriously difficult to fabricate during hot and cold work. A requirement for adding the alloy elements in this work will be that the interaction between them will provide hardening by additional cold working, but with no occurrence of chemical interaction between them and not removing them from the solid solution. This paper aims to analyze the effect of cold working on mechanical properties of Al-0.18%Zr, Al-0.18%Zr-2.0%Mg and Al-0.18%Zr-6.0%Mg alloys compared to results obtained without cold working. The alloys were melted in a muffle furnace and cast in a water-cooled Cu mold. Samples were machined to the diameter of 9.5 mm and then were cold worked, obtaining samples with a diameter of 3.0 mm. Tensile test were performed for mechanical characterization. The ultimate tensile strength and elongation of the alloys before and after the cold working were evaluated. The results showed that the increase in Mg content caused grain refiniment. The cold work promoted an increase of almost 100% on the ultimate tensile strength and approximately 90% reduction of the elongation. Al-0.18% Zr-6.0% Mg showed a higher elongation associated with higher strength after cold working, a result of elongation opposite that presented in the alloy without deformation.