Preschoolers commonly experience symptoms of ADHD and disruptive behavior problems. Behavioral parent management training (PMT) is an evidence-based intervention for addressing both ADHD and disruptive behaviors in this population; however, many PMT programs are burdensome in length and have limited data regarding long-term effectiveness for ADHD specific outcomes. This study examined outcomes up to 1 year following completion of a brief behavioral intervention (M = 6.51 sessions) for preschoolers. Participants were children aged 2–6 years with clinically significant disruptive behaviors and their parents. Results demonstrated significant improvements in parent-reported child hyperactivity and inattention from pre-to-post intervention, with sustained improvement at 6 months and 1 year post intervention. Teacher-reported hyperactivity and inattention also showed significant improvements from pre-to-post intervention, which were maintained across time points. These results were also found among a subset of participants with clinically significant ADHD symptoms at baseline. This study highlights the long-term effectiveness of a brief PMT program to address symptoms of ADHD and disruptive behaviors in preschoolers. Findings support the recommendation to offer PMT as a first-line intervention for preschoolers with ADHD symptoms to reduce the need for early intervention with stimulant medication and address comorbid disruptive behaviors.