This study identified critical issues in the design of a blended learning environment by examining basic design considerations and implementation issues. Following a design-based research approach with the phenomenological tradition of qualitative research, the study investigated instructor experiences relating to the design, development, and implementation processes of a blended course. The results reveal that the design considerations centred on the pedagogical approach, course organization, materials preparation, interactions, and the instructor's and students' roles. The affordances of the implementation included the arousal of the students' interest and participation, flexibility, time conservation, the ability to track student progress, and the improvement of interaction, collaboration, and communication opportunities. The challenges were increased workload, course and time management, overlaps, and the creation of harmony between the face-to-face and online environments. The overall results show that the critical issues involved context, the pedagogical framework, instructor competency, and technical issues in the blended course design.