This study examines English Medium Instruction (EMI) practices in online learning environments, comparing experiences between Malaysia (outer circle) and Japan (expanding circle) using behavioural science frameworks. The research addresses gaps in EMI literature, particularly the lack of comparative studies across different linguistic contexts and limited investigation of online EMI challenges. Using the Theoretical Domains Framework and the Capability, Opportunity, Motivation-Behaviour model, the study investigates key influences on student communication and engagement, differences between Malaysian and Japanese contexts, and support needs for online EMI contexts. Results revealed distinct differences between institutions. Malaysian university (UM) students showed higher confidence and capability in English-medium learning, with knowledge, beliefs about capabilities, and reinforcement serving as strong predictors of active participation in online classes. Japanese university (UJ) students demonstrated lower agreement levels across most domains, with social/professional identity and intentions as primary predictors. Students at both institutions showed high awareness of technical support services, though academic skills and writing support had lower usage. Among those who did use the services, evaluations were largely positive, and qualitative data suggested that low uptake reflected students' capacity to self-identify their needs and draw on alternative resources. The study suggests tailored intervention strategies for each university: UM students need enhanced reinforcement mechanisms and emotional support systems, while UJ students require a broader range of interventions targeting knowledge and skills, beliefs about capabilities, social/professional identity, and intentions to foster active participation in online EMI environments.
