Introduction: Assessing airway inflammation through sputum eosinophil counts is a crucial marker in asthma control. This study investigated the relationship between sputum eosinophil levels, asthma control, and pulmonary ventilatory function in children. Methodology: A cross-sectional study was carried out, focusing on asthmatic children aged 12 to 14 in Ho Chi Minh City. Sputum samples were collected using a hypertonic saline-induced sputum protocol and neutrophils were quantified via direct counting. A sample was classified as eosinophilic if it had eosinophils levels of ≥ 3.0%. Asthma control was assessed using the Asthma Control Test (ACT) and Global Initiative for Asthma (GINA) criteria. Spirometry was employed to assess lung ventilatory function. Results: Out of 47 qualified sputum samples, 10 were categorized as eosinophilic, while the remaining were non-eosinophilic. Among subjects with eosinophilic sputum, 60.0%, and 40.0% were well-controlled according to GINA and ACT criteria, respectively. The mean forced expiratory volume in one second (FEV1) was 83.9 ± 9.0% in subjects with eosinophilic sputum and 91.1 ± 11.7% in those without. The difference in FEV1 between the two groups was not statistically significant (p = 0.079). Additionally, no significant association was found between ACT and GINA criteria with sputum eosinophil counts (p > 0.05). Conclusion: Our findings suggest that the presence of eosinophil in the sputum samples is not associated with asthma control in children. Further research with larger sample sizes is necessary to explore the association between sputum eosinophil counts, asthma control, and indirect indicators.