Measurement of eosinophilic airway inflammation can assist in the diagnosis of allergic asthma and in the management of exacerbations, however its clinical implementation remains difficult. Galectin-10 has been associated with eosinophilic inflammation and has the potential to be used as a surrogate biomarker. This study aimed to assess the relationship between galectin-10 in sputum with sputum eosinophil counts, the current gold standard of eosinophil inflammation in the lung. Thirty-eight sputum samples were processed for both eosinophil counts by cytospins and semi-quantitative measurements of galectin-10 by western blots. A strong association was observed between galectin-10 levels in sputum and sputum eosinophil measurements, and they accurately determined sputum eosinophilia. The results support the potential for galectin-10 to be used as a surrogate biomarker of eosinophilic airway inflammation.