Background: Despite parallel increases in asthma and obesity prevalence, there is little data on obesity as a risk factor for atopy. The latter is an important phenotype in asthmatic patients. This study investigates the association between asthma traits, atopy and obesity-related markers in Chinese adolescents. Methods: 486 schoolchildren were recruited among participants of our population-based study on the epidemiology of obesity, and their allergy status was ascertained using a standardized questionnaire. Subjects’ anthropometry was recorded on-site, and fasting blood was collected for allergen-specific immunoglobulin E (IgE), lipids and systemic inflammatory biomarkers. Results: 98 (20.2%) subjects were classified as overweight or obese. Obesity status was not associated with asthma, allergic rhinitis or eczema (p > 0.25). Atopy was not associated with age-adjusted body mass index (BMI) or waist circumference. Atopy and presence of allergen-specific IgE did not differ between overweight or obese children and those with normal BMI (p > 0.25), although subgroup analysis suggested that cockroach sensitization was more common among males who were obese or overweight (p = 0.045). White cell count (WCC) was higher among atopic than nonatopic children (mean values 6.5 × 109/l vs. 6.2 × 109/l, p = 0.006). Logistic regression revealed WCC to be the only risk factor for atopy (OR 18.97, p = 0.004). Conclusions: Obesity is not associated with asthma or atopy in Chinese children. High WCC is an important risk factor for atopy in both males and females. Gender does not exert any consistent effect on the association between obesity and allergen sensitization in children.