Event-related potentials were used in this study to investigate the neural correlates of prospective memory and whether working memory is involved in prospective remembering. Thirty undergraduate or graduate students participated in the study. All participants completed a working memory test, namely, the Chinese Letter-Number Span Test, and were divided into two groups: the longer and shorter working memory span groups. They also undertook a prospective memory task while electrophysiological data were recorded. The results showed that participants in the longer working memory span group had shorter reaction times and smaller amplitudes in prospective positivity than participants in the shorter working memory span group. The results suggested that working memory resources are involved in the intention retrieval process of prospective remembering.