While hypoxia (i.e. low dissolved oxygen level in water) events occur naturally, global change and human activities have exacerbated their strength and temporal fluctuations. As populations may not be able to escape the hypoxic conditions, it is crucial to understand how organisms can adjust and adapt to these fluctuating environments across generations. When directly exposed, individuals may be able to adjust their phenotypes through plasticity to maintain their fitness. With continued exposure to hypoxia over generations, adaptive transgenerational plasticity can take place to help the offspring to survive the new conditions. Even longer exposure could also lead to the evolution of the population. However, so far, little is known on how plastic response to hypoxia could actually pave the way for future evolution. Using two populations of three-spined sticklebacks (Gasterosteus aculeatus) collected from streams already experiencing and potentially adapted to strong hypoxic events or not, we exposed the offspring to experimental hypoxia (30% air saturation during the night and 100% during the day) over three generations, resulting in several groups reflecting within-, inter-, and trans-generational plasticity, as well as adaptation. We then measured their growth, metabolism, and behaviour and highlighted that the plastic responses observed were not necessarily in line to the potential adaptation. While the directions of the responses were different, we cannot exclude that the fish plasticity might still be a strategy to cope with the environment until genetic adaptation occur.