Flexibility is a key skill to deal with unexpected emergencies. However, successful flexible behaviour can necessitate different types of cognitive and behavioural changes depending on the current task demands. For example, sometimes we might have to flexibly shift our attention (sensory flexibility), alter our actions (motor flexibility), or change our task goals (goal flexibility). So far, it is unclear if flexible alterations of different aspects of cognitive functions rely on a same, shared set of mechanisms (e.g., a general “flexibility network” in the brain) or several domain-specific mechanisms depending on the kind of change we need to implement. Across two studies (N = 40/N = 35), we used EEG to measure neural oscillations during demanding reaction time tasks where we independently manipulated the need to either flexible change attentional focus, motor actions, or task goals. Behaviourally, in line with previous studies, we found that the need to flexibly change either of these aspects interfered with participants’ performance. Importantly, on a neural level, we found that each type of change was associated with the same pattern of neural reactivity. More specifically, independent of the type of change, the need to alter behaviour was associated with higher frontal theta power and lower posterior alpha power. Importantly, these patterns of neural reactivity were predictive of participants’ performance in flexibly changing their behaviour. Thus, our studies provide evidence that there is a general neural mechanism that underlies the fundamental human ability to flexibly change one’s behaviour to adapt to changing environmental demands.