Proper nouns constitute a lexical class with special properties and are thus treated differently from other words by second language acquisition researchers. An assumption exists that even low-proficiency learners will find them unproblematic, yet research suggests this assumption might be misplaced. The present study involved two self-paced reading experiments designed to investigate proper nouns' influence on Japanese university students' reading fluency. In Experiment 1, participants were presented with 60 decontextualized sentences containing 30 proper nouns and 30 common nouns to determine whether they are processed in a similar manner. In Experiment 2, participants read another 60 sentences comprising a book chapter to explore the effects of repeated exposure to a set of proper nouns. The results indicated that proper nouns are processed in a similar manner to common nouns in terms of disrupting reading fluency. The implications for language learning pedagogy, in particular extensive reading, are discussed.