This qualitative study investigated the need for transitional mental health services for young people aged 16-19 years in a health district, as perceived by professionals from mental health, social, education and non-statutory services. Semi-structured interviews with 39 managers and practitioners who planned or provided services for this age range, from a wide range of agencies, explored issues related to older adolescents' needs, service communication, transfer arrangements, current gaps, and recommendations. Interviews were transcribed verbatim and themes emerged according to grounded theory. The four identified themes, with 21 categories, were: (i) older adolescents have multi-faceted needs, (ii) statutory mental health services are not geared towards this age group, (iii) communication between services is variable, and (iv) there are no formal transfer arrangements from child to adult services. The findings support the need for specialist transitional services, and the adoption of an interprofessional service model incorporating education, social services and non-statutory agencies.