The association between napping and consolidation of emotional face memory is still not well understood. In the present study, subjects of a nap and wake condition (each n = 20) were presented pictures of facial expressions in a declarative memory task and word learning was used as a control task, whereby emotional valence in both tasks was varied. Hypothesized was better memory performance for negative than neutral stimuli after a 1 h nap as well as a positive association between negative stimuli and non-rapid eye movement (NREM) sleep. Memory performance was evaluated via face recognition (old/new discrimination) and free recall of words. No enhancement of face recognition and word recall by sleep was found. However, while recall of negative words positively correlated with NREM sleep (i.e., total sleep time), the positive and linear association for recognition of negative faces was limited to the sleep stage N3 (rich in slow-wave sleep). Selective enhancement of negative facial processing by slow-wave sleep can be concluded.