The influence of different harsh environmental conditions on the fracture behaviour of secondary bonded adhesive joints is experimentally investigated using mode I DCB tests. Two types of adhesively bonded joints under wet-aged and non-aged conditions were tested at three temperatures: −55 °C, room temperature and 80 °C. The wet-aged specimens were exposed to accelerated ageing in an environmental chamber at 70 °C/85% RH for four years; meanwhile, the non-aged specimens were stored in the laboratory under controlled conditions at room temperature. It was observed that extremely long ageing time has a significant effect on the fracture response of the bonded joint, while the temperature increase is holding a slight impact. Freezing temperature leads to more brittle behaviour and a reduction in the fracture toughness.