The Vietnamese language includes vocabulary derived from Chinese called Han-Viet words (từ Hán Việt), and each Chinese character (kanji) has a Vietnamese reading, which is referred to as Han-Viet sounds (âm Hán Việt). The purpose of this study was to investigate the phonological processing of Japanese kanji words by Vietnamese learners of Japanese. In the experiment, intermediate Vietnamese learners of Japanese were asked to perform a naming task. The target Japanese kanji words were selected by manipulating the kanji consistency and the phonological similarities between Vietnamese and Japanese. The results showed that participants had longer reaction times for words having both different kanji and low phonological similarity. This indicates that L2 orthographic representation has strong links to L2 phonological representation regardless of kanji consistency and that the activation of L1 phonological representation does not affect the processing of Japanese kanji words in a naming task. This differs from Chinese and Korean learners of Japanese, in which the activation of L1 phonological representation facilitates the processing of kanji words in naming.