This study aimed to determine if an association exists in cats between serum allergen-specific immunoglobulin E (IgE) testing results and a clinical diagnosis of asthma. The study also aimed to determine whether the number of allergens with positive IgE reactivity and magnitude of IgE responses correlates with severity of clinical signs or airway eosinophilia. Eighteen cats were studied, and serum allergen-specific IgE testing supported an allergic etiology in 78% of cats, with all but 1 cat having polysensitization, indicating a strong association between detection of allergen-specific IgE and asthma in cats. The severity of clinical signs and the magnitude of airway eosinophilia did not correlate with the degree of IgE reactivity. However, positive allergen-specific IgE results may guide avoidance or elimination of sensitizing allergens.