This study aims to describe the implementation of online learning in the Scientific Writing course at Universitas Terbuka and to analyze student engagement from cognitive, affective, and behavioral perspectives. A descriptive qualitative approach was employed, involving 15 students selected through purposive sampling. Data were collected through semi-structured interviews, observation of online learning activities, and documentation, and were analyzed using data reduction, data display, and conclusion drawing, supported by source and technique triangulation. The findings indicate that online learning was systematically implemented through the use of a Learning Management System (LMS), digital learning materials, discussion forums, structured assignments, and continuous instructor feedback. The implementation of online learning enhanced student engagement cognitively through improved conceptual understanding and critical thinking, affectively through increased motivation and learning comfort, and behaviorally through active participation and consistent task completion. These findings highlight the importance of interactive and student-centered online learning design in supporting the development of higher-order academic skills.