Objective: No psychosocial treatments have been developed for children with ADHD and severe mood dysregulation (SMD) despite the significant prevalence and morbidity of this combination. Therefore, the authors developed a novel treatment program for children with ADHD and SMD. Method: The novel therapy program integrates components of cognitive-behavioral therapies for affect regulation with a parent-training intervention for managing recurrent defiant behaviors. It consists of nine 105-min child and parent groups run in unison. A pilot trial was conducted with seven participants with ADHD and SMD ages 7 to 12 who were on a stable stimulant regimen. Results: Six of the seven (86%) families completed the program. Participants showed large improvements in depressive symptoms, mood lability, and global functioning. Milder improvements in externalizing behaviors were observed. Conclusion: Results suggest the feasibility and potential efficacy of the therapy program for children with ADHD and SMD and warrant a larger controlled trial. (Contains 3 tables.)