AbstractThis paper looks at the acquisition of the vocabulary used in daily conversation by advanced level English speaking learners of Japanese language. Five factors which were found to affect learners’ acquisition are discussed. The aim of this paper is to discuss lexical errors made by advanced learners of Japanese and identify the factors which hinder their lexical acquisition by focusing on intralexical factors and interlexical factors. The data was obtained from interviews with fourteen advanced level students. The findings of the study reveal that interlexical divergence of semantic structure is the most common reason for advanced learners failure to acquire vocabulary in the target language. This finding highlights the difficulty learners face in comprehending the lexical semantic structure in the target language and maintaining all the lexical items which correspond to single word in their native language. Intralexical phonological similarity is also a confounding factor for learners. These findings are relevant in the context of vocabulary teaching from the aspect of facilitating learners’ semantic knowledge.