Secondary pneumothorax often occurs during the clinical course of interstitial pneumonia, but few reports exist. Previous studies have shown that corticosteroids (CS) may be associated with the incidence of pneumothorax, although this is still unclear. Twenty-nine secondary pneumothorax patients (23 men and 6 women) with interstitial pneumonia who presented at our institution from 2001 to 2012 were reviewed. Patients with pneumothorax caused by medical treatment, such as mechanical ventilation or lung biopsy, were excluded. The patients were classified into two groups: those who had received CS therapy (CS group, n=14) and those who had not received CS therapy (non-CS group, n=15). No significant differences were evident in the sex, age, smoking history, and classification of interstitial pneumonia between the CS group and the non-CS group. Radiological findings revealed that fibrosis predominant in the upper lobe was more common in the non-CS group (21% vs. 60%, p=0.04). With regard to pneumothorax treatment, patients who received invasive treatment, such as chest drainage and surgery, totaled higher in the CS group (64% vs. 20%, p=0.02). Furthermore, the incidence of refractory pneumothorax was significantly higher in the CS group (29% vs. 0%, p=0.03). Interstitial pneumonia patients with upper-lobe predominant fibrosis tend to develop secondary pneumothorax during the clinical course even without receiving CS therapy. CS may be correlated with the incidence of pneumothorax in some patients, and pneumothorax is refractory under CS therapy. Therefore CS must be administered with care in such patients.