Phonemic awareness (PA) accounts for individual differences in early reading achievement in English as a first language (L1), but its effect generally fades with age. However, in English as a second language (L2), PA may still explain variation in reading ability among the adult population, depending on the readers' L1 background. We examined the role of PA in the reading comprehension of L1-Japanese readers to closely examine the relationship between PA and reading comprehension. A path analysis revealed that PA makes an indirect contribution to reading comprehension through decoding, which along with vocabulary knowledge directly supports reading comprehension. The present study provides evidence for a role, albeit indirect, played by PA in L2-English reading by L1-Japanese adult readers, and thus lends support to the understanding of the importance of fundamental phonological processing in L2 reading.