Using the theoretical framework of Guido Möllering conceptualising trust as a mental process composed of three elements—expectation, interpretation and suspension—we examined the role of trust in relation to young children’s (age ≤ 7 years) psychosocial needs when diagnosed with type 1 diabetes. Based on qualitative interviews with health care professionals (HPCs) from paediatric diabetes clinics in all regions of Denmark, we identified four main themes: trust through meaningful interaction, trust as a key factor at the time of diagnosis, trust in a long-term perspective and caregivers as the bridge to trust. We conclude that trust between young children and HCPs is central to children’s psychosocial experience, as well as a primary need, when children are diagnosed with type 1 diabetes. Trusting relationships counteract children’s experience of fear, anxiety and needle phobia and reinforce HCPs’ experience of providing good psychosocial as well as medical care. The present study offers insights into how trust can positively affect young children’s experience of diagnosis. This study also points out some key barriers to and facilitators of creating trusting relationships. This research is a first step towards a greater understanding that can inform collective future guidelines on the psychosocial care of young children.