Although research has always related e-portfolios to self-regulated learning, recently agency, which includes individual, relational, and contextual domains, has also been highlighted. Likewise, agency has been explored in technological environments that support collaborative and co-design learning processes. This study, investigating the enactment of student agency within e-portfolio learning co-design with 68 secondary students in Hong Kong, focuses on how students perceive their agency within a co-design e-portfolio learning framework, which was coined as the Co-PIRS model in previous stages of research. With descriptive aims, a mixed research methodology was designed using quantitative and qualitative data collection instruments. Among the findings, it is argued that students report a greater awareness of agency, characterized by competence beliefs (individual domain) in the showcase phase of e-portfolios, peer learning (relational domain), and the opportunities to make choices (contextual domain) in the implementation phase. The study also reveals students' positive attitudes towards reflection, which suggests the suitability of structuring collaboration in the co-design approach. These insights serve as a foundation for implementing e-portfolio co-design frameworks to empower students' agency and provide educators with guidance in Secondary Education and beyond. [Note: The page range (190-203) shown on the PDF is incorrect. The correct page range is 190-202.]