The purpose of this study was to examine the effect of the intensity of word exposure on expressive word learning and to find a better predictor for word learning between vocabulary skills and working memory (WM) during book reading intervention. Twenty-five children aged between 4 to 6 participated in this study. Standardized receptive and expressive vocabulary tests and three WM tasks (nonword repetition, word list recall, and matrix) were administered. The book reading intervention was provided using four books, with 2 different condition varying number of exposures of target words, which was 12 and 24 exposures, respectively. The number of acquired words of each condition was compared through a paired t-test and a stepwise multiple regression analysis were used to find predictors of word learning. The number of acquired expressive words was significantly higher in 24 exposures compared to 12 exposures. Word list recall and matrix scores significantly predicted expressive word learning in 12 exposures, and word list recall and expressive vocabulary scores predicted expressive word learning in 24 exposures. These results confirm the effects of repeated exposure on word learning and indicate that the factors that predict expressive word learning could be vary depending on the intensity of word exposure.