There is currently an increasing interest in the acquisition of reading fluency. This is characterized as automated reading with higher rates of speed and accuracy that enables the reader to carry out processes of higher-level comprehension. A key factor in reading fluency is the establishment of word representations in the reader’s lexicon, which allow the direct visual recognition of words. It is widely accepted that a repeated visual exposure to novel words is needed to construct these mental representations. However, the nature of memory traces reached after this training is a question hotly debated in behavioral literature. While some authors argue that a simple visual training enables the formation of lexical traces for novel words, others argue that a training not only in orthographic but also in other word features (such as phonology or meaning) is required for the acquisition of high quality lexical representations. The use of more suitable measures for exploring the brain response during this process could contribute to solve this question. In this sense, the ERP approach emerges as a powerful tool to study the neurophysiological mechanisms underlying the acquisition of the lexical reading, and particularly the training conditions under which the formation of high quality lexical representations is possible. In this paper, the main contributions from the ERP literature to the understanding of the novel word lexicalization are reviewed.