Between 12 and 14 months infants switch from slow to fast word learning mode. The neural processes involved in this development are largely unknown. This study explored the brain activity related to the fast learning of object–word mappings in 14-month-old infants. After four repetitions of eight object–word pairs, two priming effects known from earlier infant event-related potential studies were observed: word form priming indexed by the fronto-lateral negativity in the 200–500 ms range and semantic priming indexed by the parietal N400. These neurophysiological correlates suggest that infants have learned object–word mappings by four presentations. In a test phase applied at least 1 day later, the N400 differentiated between trained congruous and incongruous pairings, which indicates that this newly established referential knowledge has been consolidated in memory.