Background: Toothbrushing, limiting intake frequency, and scheduled visits to an oral healthcare professional (OHP) are key for good oral health. We aimed to explore factors influencing these oral health behaviours in Dutch adolescents with mild to borderline intellectual disabilities (MBID) in residential care. Method: Using a qualitative, descriptive approach, we conducted focus groups and interviews with 12 adolescents, 9 counsellors, and 6 OHPs. Thematic analysis mapped factors influencing adolescents' knowledge, attitude, planning, and execution of oral health behaviours to oral care stakeholders. Results: Of nine identified influencing factors, three were pivotal: Structure (influencing toothbrushing and intake frequency), Anxiety (impeding dental visits), and Support (provided by counsellors). Conclusions: Counsellors should provide structured daily guidance on oral hygiene and diet for adolescents with MBID, while respecting the adolescents' autonomy. As intermediaries between adolescents and OHPs, counsellors are key in reducing dental anxiety. Counsellors need clear oral health policies within care facilities to address competing priorities.