Background: Omalizumab, a monoclonal antibody targeting immunoglobulin E (IgE), is approved for adults and adolescents (12 years or older) with chronic spontaneous urticaria (CSU) that does not respond to high-dose antihistamines. In Korea, there is limited research on predictive biomarkers for omalizumab response in CSU patients. Objective: This retrospective, single-institution study aimed to identify clinical parameters predicting omalizumab response in Korean CSU patients. Methods: We analyzed records of CSU patients aged 19 or older starting omalizumab between January 2017 and October 2019. Omalizumab efficacy was assessed using the Urticaria Activity Score summed over 7 days (UAS7), categorized as well-controlled, mild, moderate, or severe.Ninety CSU patients participated in this study. Results: Among these, improvements in UAS7 categories from baseline to 12 weeks of treatment were observed in 78 patients, while 12 patients showed no significant efficacy. The present study identified potential biomarkers that could predict a patient’s response to omalizumab, including disease duration and total serum IgE levels (p=0.022, p=0.046). Notably, a significant correlation was observed between higher detection rates in multiple antigen simultaneous test (MAST) food testing and lower treatment responses (p=0.033). Conclusion Shorter disease duration of CSU and elevated initial serum total IgE level may serve as potential predictive biomarkers for the responsiveness to omalizumab. Furthermore, a higher MAST food detection rate seemed to correlate with a less favorable treatment response, suggesting patients with a high MAST food detection rate might benefit from a food evaluation in addition to omalizumab treatment.