Purpose: The purpose of this study is to contribute to knowledge of teachers’ relational competence with respect to students with ADHD. In addition, a specific focus is investigating whether teachers’ understanding of relational competence, regarding the targeted student group, can be developed using video-based interventions. Moreover, a focus is to examine whether - and if so how - the intervention contributes to changes in teachers as well as their students’ perceptions of their teacher-student relationshipin practice. Sub-studies: This dissertation contains four sub-studies, each of them aiming to answer a part of the overall research question. The first study is a systematic literature review aiming to systematically identify, critically review and synthesize existing research in the focused area. The second study is a pilot study investigating if teachers’ relational competence can be developed using video-based interventions. In study three, the aim was to investigate how teachers’ understanding of relational competence with respect to students with ADHD were developed using video-based interventions. Finally, the fourth study investigated if the video-based intervention (Study 3) contributed to changes in teachers’ and students’ (with and without NPS) perceptions of their teacher-student relationship. Theory: This dissertation takes its point of departure from a relational framework using Scheff’s (1997) theory of social bond together with Aspelin’s (2018) and Aspelin and Jönsson’s (2019) Relational Competence Model (RCM). The relational framework is supplemented by Laveand Wenger’s (1991) sociocultural theory of situated learning. Method: The overall design of this dissertation is based on mixed methods. An exploratory multi-stage evaluation design has been used. Characteristic of such a design is that each sub-study contains a study of its own which is iteratively following from the previous in order to evaluate the effect of the intervention made, and by extension, answering the overall research question. Knowledge contributions: The overall knowledge contribution of this dissertation concerns teachers’ perceptions of relational competence regarding students with ADHD, and how such perceptions can be developed. One of the dissertation’s scientific knowledge contributions is its testing ofthe RCM model for students with ADHD. The results indicate that the model can be successfully used to develop teachers’ relational competence towards these students. The dissertation also suggests that teachers need to have a “relational preparedness” - a readiness - for the unforeseen. This implies an ability to observe student behavior and reflect on what it suggests regarding students’ thoughts and feelings, together with the teacher’s ability to self-reflect with the intention to identify and acknowledge their own emotional reactions to student signals. Limitation: The lack of a randomized sample affects the credibility of the study. The lack of qualitative student interviews can be seen as a limitation as the information collected exposes changes in students’ perceptions but does not provide a deeper understanding of what the changes consisted of. Practical implications: The results are relevant for teacher education by providing a clear focus on teachers’ relational competence regarding students with ADHD, which, in turn, can help future teachers to be better equipped to meet the diversity of students in each classroom. Furthermore, the results should be relevant for teachers as well as school leaders, through its focus is on relational competence as a situated activity, and on how this competence can be developed through a small and limited intervention.