Mold sensitivity in asthmatic patients has recently attracted clinical interest; however the links between mold sensitivity and asthma severity in the Chinese population have been poorly characterized. In this study, we assess the relationship between asthma severity and airborne mold sensitivity in a cohort of northern Chinese patients. Ninety-three non-smoking adult outpatients with asthma completed a questionnaire and underwent skin prick testing with five aeroallergens. For all patients, eosinophil cell counts, total serum IgE (sIgE) levels, and pulmonary function were measured. An asthma severity score was calculated based on the patient's forced expiratory volume in one second (FEV1), number of asthma attacks, number of hospital admissions, and use of inhaled or oral corticosteroids in the past year. Ninety-three patients were divided into three groups based on the results of their allergy tests: negative results for all tested allergens (group A, n=32); positive reactions to aeroallergens including mold antigens (group B, n=41); and positive reactions to aeroallergens other than molds (group C, n=20). Patients in group B had a lower FEV1 (74.46%±23.09% predicted) compared with group A (85.52%±19.53%, P=0.023). Patients in both group B and C had elevated absolute eosinophil count (AEC) (group A: 3.12%±2.71%, group B: 5.41%±2.85%, group C: 6.1%±4.49%; group A vs. group B, P=0.008; group A vs. group C, P=0.002), and total sIgE values (group A: 117.36±144.90 IU/mL, group B: 195.86±155.87 IU/mL, group C: 253.31±152.41 IU/mL; group A vs. group B, P=0.031; group A vs. group C, P=0.002) compared with patients in group A. Asthma severity scores were higher in patients in group B compared to patients in group C (7 vs. 5.5, P<0.05). Patients allergic to molds were more likely to have severe asthma [odds ratio 3.636, 95% confidence interval (CI): 1.394 to 9.484; for severe versus mild asthma, P<0.05]. There was no association between asthma severity and sensitisation to house mites or weeds. Mold sensitivity is positively correlated with asthma severity in our cohort of northern Chinese patients.