Objective: Increasing evidence for the importance of several risk factors for anxiety disorders is beginning to point to the possibility of prevention. Early interventions targeting known risk for anxiety have rarely been evaluated. The authors evaluated the medium-term (3-year) effects of a parent-focused intervention for anxiety in inhibited preschool-age children. Method: The study was a randomized controlled trial of a brief intervention program provided to parents compared with a monitoring-only condition. Participants were 146 inhibited preschool-age children and their parents; data from two or more assessment points were available at 3 years for 121 children. Study inclusion was based on parent-reported screening plus laboratory-observed inhibition. The six-session group-based intervention included parenting skills, cognitive restructuring, and in vivo exposure. The main outcome measures were number and severity of anxiety disorders, anxiety symptoms, and extent of inhibition. Results: Children whose parents received the intervention showed lower frequency and severity of anxiety disorders and lower levels of anxiety symptoms according to maternal, paternal, and child report. Levels of inhibition did not differ significantly based on either parent report or laboratory observation. Conclusions: This brief, inexpensive intervention shows promise in potentially altering the trajectory of anxiety and related disorders in young inhibited children.