Attention-deficit hyperactivity disorder (ADHD) is one of the most common neurological developmental disorders in children, and sleep disorders (SDs) are a common comorbidity in children with ADHD. There are currently no pharmacological treatment options for SD in children with ADHD of preschool age (4-6 years). Repetitive transcranial magnetic stimulation (rTMS) is a novel, non-invasive neuromodulation technique. This study explores the effectiveness of rTMS for comorbid SDs in preschool-aged children with ADHD. Thirty-five children of preschool age with ADHD and comorbid SDs were recruited for this study. The children were divided into a parent behavior management training (PBMT) group (n = 19) and a repetitive transcranial magnetic stimulation combined with parent behavior management training group (n = 16). Both groups underwent 8 weeks of treatment. The children's SD scores were assessed using the Chinese Children's Sleep Habits Questionnaire, were measured before the start, at the end, and 4 weeks after the end of the intervention, and were used to measure the effects. Within-group differences were compared using a repeated-measures analysis of variance, and between-group differences were compared using an independent samples t-test and Mann-Whitney U-test. Both the PBMT group and the rTMS combined with the PBMT group significantly improved the SDs of preschool-aged children with ADHD (P < .001), but the effect of the intervention was more pronounced in the rTMS combined with the PBMT group (P < .001) and lasted longer than the PBMT group (P = .004). Repetitive transcranial magnetic stimulation is a promising non-pharmacological therapy to improve SD in preschool-aged children with ADHD.