Background: Walnuts (WN) are one of the main causes of tree nut allergies. However, the potential value of component resolved diagnosis (CRD) for WN allergy is controversial. Objective: We analyzed the clinical and immunological features of clinical WN allergy and the usefulness of CRD in young children. Methods: Forty-one participants with a history of ingesting WN who were assessed for serum-specific IgE to WN (WN-sIgE) using CRD (ImmunoCAP ISAC 112) at the Department of Pediatrics in Ajou University Hospital were enrolled and their demographic profiles, clinical symptoms, and laboratory findings were evaluated. Results: A total of 32 patients were diagnosed with clinical WN allergy, of which 31 had specific immunoglobulin E antibodies to Jug r 1 (Jug r1-sIgE). The Jug r 1-sIgE levels were higher in WN-allergic patients than in WN-tolerant patients and significantly higher in patients with anaphylaxis than in the WN-tolerant patients. Receiver-operating characteristic curves demonstrated that the Jug r 1-sIgE level was much better in discriminating between clinical WN allergy and WN tolerance in young children than the WN-sIgE level. Conclusions: Jug r 1 is the major component allergen in young children with clinical WN allergy. To measure Jug r 1-sIgE appears to be a promising approach for both diagnosis and predicting severity in young children with a history of suspected WN allergy.