Introduction: Childhood obesity has become a global public health concern in the past decade. The purpose of this study was to explore the effectiveness of an online combination exercise intervention in improving the physical and mental health of obese children.Methods: This study adopted a one-group pre-test and post-test research design. A total of 28 obese children from 6 elementary schools in Heze City, Shandong Province, China, were recruited. All participants received an 8-week online combination exercise intervention and were tested at a three-month follow-up. Participants were tested and surveyed regarding their demographic, feasibility, and obesity indicators using mental health and quality of life questionnaires. The data were statistically analyzed using a one-way analysis of variance with repeated measures.Results: A total of 26 obese children (Meanage = 10.15 years) completed the study. The retention rate was 92.9% for the entire trial (two obese children withdrew due to their inability to exercise) and no adverse events were reported. In addition, the obese children completed 25/32 (78.1%) of the online courses. After 8 weeks of the intervention, the changes in the body fat percentage of the obese children [mean difference (MD) = –3.126, p < 0.001, Cohen’s d = –1.777], thinking dimension score (MD = 1.654, p < 0.001, Cohen’s d = 0.603), total quality of life score (MD = 6.385, p < 0.05, Cohen’s d = 0.610), and work attitude dimension score (MD = 1.346, p < 0.001, Cohen’s d = 0.744) showed significant differences compared to the baseline. However, no significant differences were identified between the post-intervention and three-month follow-up measurements (p > 0.05), and we assumed that the intervention effect was maintained three months after the intervention.Conclusion: An online combination exercise intervention is a safe and feasible option to improve the mental health and quality of life of obese children and may have long-term health benefits.