OBJECTIVE: The WHO has argued that adolescent-responsive health systems are required. Developmentally appropriate healthcare (DAH) for young people is one approach that could underpin this move. The aim of this study was to explore the potential for DAH to become normalised, to become a routine, taken-for-granted, element of clinical practice. DESIGN: Qualitative ethnographic study. Analyses were based on procedures from first-generation grounded theory and theoretically informed by normalisation process theory. SETTING: Two tertiary and one secondary care hospital in England. PARTICIPANTS: 192 participants, health professionals (n=121) and managers (n=71) were recruited between June 2013 and January 2015. Approximately 1600 hours of non-participant observations in clinics, wards and meeting rooms were conducted, alongside 65 formal qualitative interviews. RESULTS: We observed diverse values and commitments towards the care of young people and provision of DAH, including a distributed network of young person-orientated practitioners. Informal networks of trust existed, where specific people, teams or wards were understood to have the right skill-mix, or mindset, or access to resources, to work effectively with young people. As young people move through an organisation, the preference is to direct them to other young person-orientated practitioners, so inequities in skills and experience can be self-sustaining. At two sites, initiatives around adolescent and young adult training remained mostly within these informal networks of trust. At another, through support by wider management, we observed a programme that sought to make the young people's healthcare visible across the organisation, and to get people to reappraise values and commitment. CONCLUSION: To move towards normalisation of DAH within an organisation, we cannot solely rely on informal networks and cultures of young person-orientated training, practice and mutual referral and support. Organisation-wide strategies and training are needed, to enable better integration and consistency of health services for all young people.