This study investigates advanced Japanese language learners' abilities to infer unknown "kanji" (Chinese character )words while reading authentic Japanese texts. Data obtained from 42 English L1 students indicate that, first, although they can guess the meanings of unknown "kanji" words in context, they frequently make erroneous guesses or fail to guess at all. Second, the more proficient students can use context better than the less proficient students. Third, when reading comprehension ability is controlled, there is no difference in "kanji" inferencing ability between heritage language HL learners and non-HL learners. Fourth, when the students can pronounce the given semantically unknown "kanji" words fully or partially while reading, such phonological knowledge proved to be related to successful inferencing.