Numerous studies have demonstrated that visual STM (VSTM) and attention are tightly linked processes that share a number of neuroanatomical substrates. Here, we used repetitive TMS (rTMS) along with simultaneous EEG to examine the causal relationship between intraparietal sulcus functioning and performance on tasks of attention and VSTM. Participants performed two tasks in which they were required to attend to or remember colored items over a brief interval, with 10-Hz rTMS applied on some of the trials. Although no overall behavioral changes were observed across either task, rTMS did affect individual performance on both the attention and VSTM tasks in a manner that was predicted by individual differences in baseline performance. Furthermore, rTMS also affected ongoing oscillations in the alpha and beta bands, and these changes were related to the observed change in behavioral performance. The results reveal a causal relationship between intraparietal sulcus activity and tasks measuring both visual attention and VSTM.