Background: The methacholine challenge test (MCT) is necessary for the diagnosis of asthma, but it is usually performed in tertiary hospitals. Fraction exhaled nitric oxide (FeNO) is an eosinophilic airway inflammation marker, can be easily performed in primary care. We aimed to investigate the sensitivity and specificity of FeNO, allergosorbent test, and serum immunoglobulin E (IgE) level in the diagnosis of mild asthma. Methods: We analyzed 64 mild asthma patients who were diagnosed with MCT between Jan 1, 2021 and Dec 31, 2022. All patients underwent FeNO, allergosorbent test, and serum IgE level before MCT. We evaluated the sensitivity and specificity of the markers, which included elevated FeNO (> 25 ppb), positive allergosorbent test, and high serum IgE level (> 100 IU/mL), in the diagnosis of asthma. Results: Out of the 64 patients, 56 had a positive MCT, while 8 had a borderline MCT. Among MCT positive mild asthma patients, the diagnostic sensitivity and specificity of combining two of three markers, elevated FeNO and positive allergosorbent test, were 0.55 and 0.87. The diagnostic sensitivity and specificity of combining two of three markers, elevated FeNO and high serum IgE level, were 0.45 and 0.82. The diagnostic sensitivity and specificity of combining three markers, elevated FeNO, positive allergosorbent test, and high serum IgE level, were 0.45 and 0.90. These results were similar in patients with borderline MCT, showing moderate sensitivity and high specificity. Conclusions: Combination of those markers may be useful diagnostic tools in patients with mild asthma, particularly those with a borderline MCT.