Background: Newly emerging Western style economic systems provide new opportunities to study the prevalence and predictors of childhood obesity. We also provide for the first time a national study of childhood obesity using all three international anthropometric criteria. Methods: The sample included 4097 Montenegrin children, 2076 boys (50.7%) and 2021 girls. Anthropometric measurements were performed in school. The questionnaire for parents included questions on 24 potential contributing factors for childhood obesity. Nutritional status was assessed according to World Health Organization, US Center for Disease Prevention and Control and International Obesity Task Force (IOTF) criteria. Results: Overall percentage of Montenegrin children who are overweight or obese (IOTF) is 22.9% of which 5.3% are obese (7.0% boys vs. 3.5% girls). We found 10 factors to be independently associated with child obesity. Positive relations [odds ratio (95% confidence interval)] were found with maternal obesity [2.05 (1.68–2.51)], paternal obesity [1.67 (1.32–2.10)], paternal employment [1.40 (1.12–1.74)], maternal smoking [1.32 (1.08–1.61)], obesity at birth [1.33 (1.04–1.70)] and computer game playing [per hour—1.11 (1.00–1.24)]. Negative relations were found with female gender [0.64 (0.53–0.78)], the number of siblings [0.88 (0.78–0.98)], birth order [0.73 (0.64–0.83)] and age [0.92 (0.88–0.98)]. Conclusion: One out of four Montenegrin children is overweight, with two times more frequent obesity among boys compared with girls. Some previously salient predictors did not appear salient in this sample. To enable worldwide comparability, we propose the use of all three childhood obesity criteria in national studies.