This longitudinal multiple-case study applies Activity Theory to analyse the integration of ePortfolio into an International Baccalaureate (IB) Middle Years Programme (MYP) Sciences classroom in Hong Kong SAR, China. Activity Theory was used as an analytical framework to examine eight IB MYP 2 students' (aged 12-13) experiences of Google Sites over two academic years of face-to-face, online, and blended learning modes of teaching and learning. Two classes of 21 students were understood as one Activity System with the inclusion of ePortfolios (Tool) that affected multiple Elements. These include participating students (Subjects), classroom norms (Rules), peers and parents (Community), feedback tasks (Division of Labour), uploading and presenting digital artefacts (Object), and personal skills-based motivation (Outcomes). Qualitative data analysis of ePortfolio artefacts and semi-structured interviews at three stages of intervention revealed two secondary contradiction themes that might have impeded ePortfolio update consistency: 1) Tool-related (unawareness of Tool affordances and misplacement of resources) and 2) Community-related (unfamiliarity with Community members' roles and conflicting feedback expectations). Recommendations (Tool-related affordances and recommendations and monthly timeline with Community roles) for ePortfolio implementation in MYP classrooms are outlined. Copyright ©2023 Elsevier Science Ltd.