Abstract The present study examined L1 influence in visual L2 word recognition in the area of letter case. Whether an English word is displayed in upper- or lower-case letters may be of little significance to English native speakers, but many ESL speakers from east Asia have found it more difficult to recognize words printed in upper-case letters. Two experiments were conducted to explore two questions: (a) whether there was indeed a case effect in L2 word recognition in that ESL speakers took longer in responding to upper-case words, and (b) whether this case effect only occurred for ESL speakers whose first languages employed a script other than the Roman alphabet. The participants included English native speakers, ESL speakers whose L1s employed the Roman alphabet (the Romance ESL group) and ESL speakers whose L1s did not. They were asked to perform a lexical decision task on English words displayed in either upper- or lower-case letters. In both experiments, a reliable case effect was found for the latter ESL group only. This L1-related case effect raised both theoretical and pedagogical issues to be explored in future research.