Living with attention deficit hyperactivity disorder (ADHD) and mental illness involves an increased risk of lifestyle-related diseases. Although there are several ways to provide support to adult persons with ADHD, there is a lack of non-medical strategies for this purpose. This study explore how adult persons with ADHD with mental illness experienced taking part in a nurse-led lifestyle intervention. Fifteen participants participated in a 52-week lifestyle intervention. The analysis revealed two main categories; Building trusting relationships and Health together. This nurse-led lifestyle intervention could be an alternative or complement to current approaches to promoting health in adults with ADHD.