Emotional meaning impacts word processing. However, it is unclear, at which functional locus this influence occurs and whether and how it depends on word class. These questions were addressed by recording event-related potentials (ERPs) in a lexical decision task with written adjectives, verbs, and nouns of positive, negative, and neutral emotional valence. In addition, word frequency (high vs. low) was manipulated. The early posterior negativity (EPN) in ERPs started earlier for emotional nouns and adjectives than for verbs. Depending on word class, EPN onsets coincided with or followed the lexicality effects. Main ERP effects of emotion overlapped with effects of word frequency between 300 and 550 ms but interacted with them only after 500 ms. These results indicate that in all three word classes examined, emotional evaluation as represented by the EPN has a post-lexical locus, starting already after a minimum of lexical access.