The durability of construction materials is one of the most important properties related to their sustainability and longevity. With various degrading factors, including carbonation, chloride and sulphate attack, water ingress and cycles of temperature change, there is a wide area for improvement for modern construction materials. The use of carbon nanotubes in cement-based materials has the potential to create stronger, functional materials which combine better mechanical properties with functionality as a strain sensor or heating material. However, the question of the durability of cement nanocomposites under various factors is still not fully recognised. The presented research aims at assessing the resistance of cement mortars infused with different dosages of carbon nanotubes to rapid ageing cycles. Repeating cycles of high and low temperatures with wind and light exposure using an ageing chamber were employed to simulate the ageing process of cement mortar samples without other corrosive factors. A comparison of mechanical strength differences for samples exposed to rapid ageing and the control group was used to determine the effect of carbon nanotube addition and dosage on the materials’ durability. The results show that a higher addition of carbon nanotubes leads to the smaller reduction of compressive strength after cycles in the ageing chamber with 0.2wt.% dosage of carbon nanotubes, resulting in a smaller compressive strength reduction than for the reference sample. The flexural strength of samples increased after exposure, which could result from re-occurring hydration caused by high temperatures and humidity in the ageing chamber.