Working memory (WM) processes decline with increasing age. According to recent concepts, it is necessary to differentiate between dynamically changing ‘WM states’ which are regulated via gating mechanisms. We investigated which neural oscillatory processes underlying WM gating and updating are affected by age with a focus on alpha and theta band activity. With an EEG beamforming approach, we examined the data of N = 132 healthy individuals aged 18–76 years who performed the reference-back paradigm. Using mediation analyses we analyzed whether alpha and theta band activity can explain age-related effects on WM gate opening, gate closing, and updating processes at the behavioral level. The data showed that alpha band activity mediated the relationship between age and all three core WM processes, primarily reflected in slower and less efficient switching among WM states with increasing age. Theta band effects did not mediate age-related effects on WM dynamics. The likely reason why alpha band activity is particularly involved in age-related effects on WM functions may lie in its superordinate role, which facilitates the coordination of suppressing distractions and maintaining relevant information in the WM. Alpha band activity might therefore be mechanistically relevant for counteracting WM decline during aging.