This study aimed to investigate complaint-making strategies used by Japanese and Thai learners of English. Complaining, an expression of dissatisfaction or disapproval toward others’ past or ongoing actions, is a highly face-threatening act. However, previous studies have paid less attention to this speech act as compared to other major speech acts, such as requests. Additionally, given that English is used as a global language, in an English-as-a-Lingua-Franca environment, it is important to examine whether L2 learners with different L1/cultural backgrounds use similar or different complaint-making strategies. In this study, Japanese and Thai university-level learners of English took a discourse completion test (DCT), which manipulated social status (power) and mental distance (distance). The DCT comprised four situations in academic contexts (e.g., complaining about an essay grade to a professor). Data were analyzed regarding the frequency of linguistic characteristics appearing in core information called head acts and surrounding information called supportive moves. Further, the sequential organization of explicit complaints in complaint-making strategies was also analyzed as a way of identifying culture-specific patterns of preference organization. Preliminary analysis indicated that Thai learners expressed complaints more directly, whereas Japanese learners tended to use more supportive moves before producing the head act. These results suggest that different L1/cultural backgrounds influence L2 speech act performance. The present study contributes to our understanding of the social and sequential organization of talk in cross-cultural interactions and its potential effects on intercultural miscommunication.