Aim The aim of the study was to qualitatively investigate the adolescents' need for professional support when a parent has amyotrophic lateral sclerosis (ALS) – from the adolescents' and the parents' perspectives.Methods A total of 37 individual semi-structured single interviews with 18 families were conducted, including 11 adolescents aged 8-25 and 26 parents, 13 with ALS and 13 co-parents. Data was analysed using qualitative content analysis.Results Both adolescents and parents described the adolescents as needing professional support but found it difficult to articulate this need. However, the results indicate that the adolescents needed help in bringing manageability into their lives due to the uncertainty of living with the illness in the family. It was therefore essential to ensure that the adolescents were not forgotten in the disease context and that their needs for being involved as well as for obtaining information and understanding, was addressed. The importance of offering the adolescents support early was emphasized, but also of actively helping the families to master challenges in their everyday life. Support adapted to each family's unique situation and preferences was desired, as the adolescents' need for support seemed to be individual, disease-dependent and varied during different phases.Conclusion Given the adolescents' need for information and understanding, healthcare professionals must actively work to reach the adolescents as early as possible. It is crucial to ensure that the adolescents are given the opportunity to be involved based on their own conditions, as well as to support the families to strengthen their communication.