This study aims to assess whether 12 sessions of indigenously adapted cognitive-behavioral therapy for excessive smartphone use (IACBT-ESU) would reduce excessive smartphone use. A single-blind randomized controlled trial was conducted in students (12 to 19 years of age) to examine the potential beneficial effects of IACBT-ESU (n ϭ 62) compared with brief educational data alone (n ϭ 62). Symptoms of depression, anxiety, stress, and peer relations were also compared between the two groups. The IACBT-ESU group demonstrated significant reductions in excessive smartphone use, with reduced symptoms of depression, anxiety, stress, hyperactivity, and emotional difficulties at both trial end and at 3-month follow-up (p Ͻ .01) compared with control participants. IACBT-ESU was associated with reduced excessive smartphone use and improved psychological well-being, with beneficial findings maintained 3 months after the trial's end.