This study analyzes the importance of selecting adequate picture books to facilitate the acquisition of new vocabulary with young EFL learners, taking into account the complexity of the narration, the complexity of the illustrations, and the appropriate number of sessions. The study was conducted with a class of twenty-two 3-year-old students at a charter school in Madrid, Spain. Results showed that students learned more vocabulary when the narration consisted of simple sentences or single words and when the books had at most three elements per page, with a clear distinction between those elements and the background. This study shows the importance of making a good selection of picture books to be used as a tool in the EFL class and offers the possibility for further studies with a bigger sample, also analyzing factors such as the length of the books and the number of target vocabulary words considered.