Introduction: Health promotion MOOCs (hpMOOCs) can be designed to educate general audiences on global health issues and provide accessible evidence-based content. Thus, it is essential to assess the instructional design quality of hpMOOCs through more than one perspective to ensure course participants have an effective learning experience and their learning needs are met. Methods: Our study involved a comprehensive exploration of an hpMOOC about dementia risk reduction with sustained massive reach and established impact. To fully understand the quality of this course, instructional design elements were assessed from an instructional designer lens and a course participant lens. The designer lens involved a detailed review of the quality of the course against a recognized quality rubric. The participant lens involved topic modeling and thematic analysis of 1,531 responses to a feedback survey item in order to identify design elements preferred by participants. Results: While the course performs well and meets most quality standards, it falls short of fully meeting the criteria set by the rubric. However, the rubric could be further developed to better facilitate the quality assurance of hpMOOCs. The participant lens reveals the course meets participants' expectations and it offers two new avenues for enhancing the current presentation of course content. Conclusion: Assessing the quality of hpMOOCs through a dual lens provides triangulation that helps to gain a more comprehensive understanding of how to improve their instructional design quality.