The behaviour of carbon fibre reinforced polymer-confined cylindrical and prismatic concrete specimens subjected to several different environmental conditions was investigated in four groups. The first group of specimens was used as a reference. In the second group, specimens were exposed to dry heating-cooling (H-C) cycles in the environmental test chamber (ETC), whereas specimens in the third group were kept in water while simultaneously being subjected to H-C cycles in the ETC. Finally, the last group of specimens was kept outside of the laboratory to determine the outdoor environmental effect. After the ageing phase, specimens were tested under monotonic uniaxial loading to determine the change in their mechanical properties. Cylindrical specimens were observed not to be significantly affected by H-C cycles with the exception of their ultimate strain, which decreased under outdoor conditions. As for the prismatic specimens, dry H-C cycles were found to reduce strength by up to 24% and strain by up to 33%. Wet H-C cycles and outdoor exposure were seen to decrease further the strength and ultimate strain of prismatic specimens.