Twenty‐four young and 24 middle‐aged academics carried out a language recognition task in which sentences were presented that made either a high or a low demand on working memory (WM). The sentences ended either normally (i.e., congruent) or with an incongruous word. Middle‐aged subjects had smaller WM scores, a marginally slowed down recognition performance, and a smaller and delayed N400 component. The event‐related potential (ERP) difference between congruent and incongruent endings was smaller in the high‐load condition for younger subjects and totally disappeared for the middle‐aged subjects. ERPs for all subjects showed a WM‐related positivity in the middle of the sentence and a WM‐related negativity at the sentence ending. These shifts could be associated with either storage and retrieval processes or with clause wrap‐up processes. Most ERP‐effects were dependent on WM capacity. Age differences in sentence processing are not simply explained by age itself but depend to a large extent on individual memory capacity.