Background: Humidifier disinfectant‐associated children's interstitial lung disease has an unpredictable clinical course with a high morbidity and mortality. Objectives: To evaluate the differences in clinical findings between survivors and non‐survivors of humidifier disinfectant‐associated children's interstitial lung disease. To evaluate dynamic changes in serum cytokines related to inflammation and fibrosis in lung injury, and to determine whether these changes are predictive of survival in this disease. Methods: We evaluated 17 children with humidifier disinfectant‐associated children's interstitial lung disease, from whom serum samples were obtained weekly during hospitalization. The severity of chest tomographic and lung pathologic findings was scored. Levels of several cytokines were measured in the serial serum samples. Results: Seven of the 17 children were survivors. Compared to survivors, non‐survivors had greater ground‐glass attenuation on follow‐up chest tomography, higher admission neutrophil counts, and more macrophages on pathologic findings. Transforming growth factor‐beta 1 persisted at an elevated level (1,000–1,500 pg/ml) in survivors, whereas it decreased abruptly in non‐survivors. At the time of this decrease, non‐survivors had clinical worsening of their respiratory failure. Transforming growth factor‐beta 1 was positively correlated with PaO2/FiO2 (r = 0.481, P < 0.0001). Conclusions: Non‐survivors exhibited more inflammatory clinical findings than survivors. Transforming growth factor‐beta 1 remained elevated in survivors, suggesting that it affected the clinical course of humidifier disinfectant‐associated children's interstitial lung disease. The prognosis of this lung disease may depend more on controlling excessive inflammation and repairing damaged lung than on fibrosis, and transforming growth factor‐beta 1 may play a key role in this process. Pediatr Pulmonol. 2016;51:173–182. © 2015 Wiley Periodicals, Inc.