To build a culture of integrity in a HE institution, innovative approaches are needed to enhance education of research ethics and integrity (REI). In addition to educating students, understanding is needed on how to facilitate for those who lead others. The focus is on early-career researchers (ECRs) as future REI leaders. The current study sheds light on how learning and REI leadership competencies evolve during scaffolded collaborative research ethics training for this target group. The study combines new instruments as part of holistic DBR. Data was collected from 3 groups of experienced researchers attending 3 training sessions in the form of written group reports and group discussion recordings. Qualitative deductive analysis was utilised for monitoring the learning process, scaffolding patterns, and display of REI leadership principles. Also, quantitative analysis was applied to group discussion data, displaying the nature of collaboration. Results imply that collaborative case-based role play format is effective in training future REI leaders. All groups displayed high levels of understanding. Combining ECRs and researchers with leadership experience supported knowledge building in the groups by bringing in various perspectives. Even though groups required different amounts of scaffolding, the nature was similar: maintaining goal orientation, highlighting critical features and redirecting learners. Learning analytics of collaboration indicated that the person with leadership experience was not necessarily the most active participant nor took the role of a 'group leader'. Still, it was mostly that person who displayed leadership competencies thus supporting other group members to develop leadership aspects.