This study defines and analyses adaptive gamification design principles for online courses. It was conducted as a holistic single case study framed by two theoretical approaches, namely, gamification and adaptive learning. The first part of the study establishes a theoretical matrix with its contents converted into a questionnaire which includes nine semi-structured questions. Following this, a four-round Delphi panel with 12 field experts was performed. In the second part, the design principle proposition checklist was presented to a focus group of six formed by experts in the field of open and distance education to obtain their feedback on its usability, applicability and significance. The qualitative data obtained in the first phase was analysed by using content analysis while the quantitative data obtained in the other phases were analysed by calculating the distribution of frequencies and measures of central tendency. Results of the Delphi rounds and the focus group interview yielded a checklist of adaptive gamification design principles for online courses comprising 102 design principles under 11 themes.