This study aims at investigating the effects of phonological short-term memory (PSTM), learning styles, and oral repetition on middle school students" learning of English vocabulary. Two groups had different treatments (semantic learning and oral repetition) and vocabulary learning was assessed in spelling, meaning, and production twice, immediately after the learning sessions and two weeks thereafter. The results reveal that oral repetition and the PSTM capacity affected the vocabulary learning significantly, but not learning styles. The students with a higher PSTM capacity learned significantly more words but didn"t remember them better for a longer period than those with a lower PSTM capacity. No clear effects of learning styles were noted, while the PSTM capacity of auditory learners was higher than that of visual learners. The oral repetition group learned significantly more words than those who did only semantic learning, which suggests the usefulness of oral repetition in learning new vocabulary.