Prospective memory (PM), or memory to perform intended actions delayed to the future, plays a crucial role in daily tasks such as medication adherence. PM deficits commonly occur in normal aging and neurodegenerative diseases, highlighting the importance of understanding the underlying mechanisms to inform potential interventions. Brain regions active during PM tasks include the left dorsolateral prefrontal cortex (DLPFC) and inferior parietal cortex. PM tasks engage attentional networks, and changes in alpha frequency oscillations were observed during PM processing. We hypothesized that these oscillations play a causal role in the ability to remember future intentions.Transcranial alternating current stimulation (tACS) enables non-invasive modulation of neural activity and is used to investigate potential causal relationships between brain function, rhythms, and regions. We compared the effects of alpha-tACS with two control conditions – theta-tACS, to examine frequency specificity, and Sham stimulation – on both PM performance and well-established neural correlates of PM. Participants performed a 2-back working memory task, which has sufficient cognitive load to prevent continuous PM rehearsal. The PM cue was a different response to stimuli with a particular colour.Alpha-tACS significantly improved PM accuracy. Moreover, early activity in the left dorsal parietal cingulate cortex was lower after alpha-tACS compared to Sham stimulation. PM late activity was also lower in the left DLPFC compared to the 2-back task after alpha-tACS. These findings provide evidence for the involvement of alpha oscillations in PM performance and suggest the potential utility of tACS as a neuromodulatory intervention to enhance cognitive function in tasks requiring PM.