This study explored how the first language (L1) influences discourse marker use in second language (L2) speech. Some studies (e.g., Liu, 2013; Sankoff et al., 1997) have addressed the issue of L1 transfer of discourse markers in L2 speech, suggesting that non-native speakers' L1 use may influence the frequency and usage of English discourse markers in their speech. However, only a few detailed studies have investigated L2 learners' use of discourse markers under the influence of their L1. To compensate for these shortcomings, this study examines whether Japanese speakers' L1 use influences their use of English discourse markers in speech. Two experiments were performed with Japanese college students using a question-and-answer task, a short speech task, and a picture description task. The results of the quantitative and qualitative analyses suggest that the use of some Japanese discourse markers may be transferred to the use of some English discourse markers such as "and, so," and "but" in each task. Additionally, differences were observed in the items used as discourse markers in both English and Japanese by task.