Objective: To test the acceptability, satisfaction, and effectiveness of a web-based intervention for teachers of elementary school–aged children with ADHD. Method: Elementary classroom teachers (N = 58), along with their students with ADHD, participated in a randomized controlled trial. The program consisted of six sessions that included evidence-based intervention strategies for reducing ADHD symptoms and impairment in the classroom setting. Teachers also had access to a moderated Discussion Board and an online ADHD coach. Questionnaire data were electronically collected from teachers and parents pre-intervention, post-intervention (6 weeks), and after an additional 6-week follow-up. Results: Intent-to-treat analyses found significant improvements based on teacher (but not parent) reports of core ADHD symptoms and impairment for the Teacher Help for ADHD treatment group. Teachers reported a high level of acceptability and satisfaction. Conclusion: Web-based ADHD interventions have the potential to reduce the barriers to treatment utilization and implementation that are common problems for school-based ADHD interventions.