The role of second-line chemotherapy in patients with non-small cell lung cancer (NSCLC) and preexisting interstitial pneumonia (IP) previously treated with platinum-based chemotherapy remains uncertain. This study was conducted to elucidate the efficacy and tolerability of second-line docetaxel monotherapy for patients with platinum-refractory advanced (stage IIIB, IV, or relapse) NSCLC and preexisting IP. A total of 35 patients (median age, 67years) treated with docetaxel monotherapy in a second-line setting following first-line platinum-based chemotherapy between January 2002 and December 2013 were retrospectively reviewed. The overall response rate and disease control rate were 8.6% [95% confidence interval (CI) 0-17.9%] and 37.1% (95% CI 21.1-53.1%), respectively. The median progression-free survival and median overall survival periods were 1.6months (95% CI 1.2-2.0months) and 5.1months (95% CI 3.2-6.7months), respectively. The incidence of acute exacerbation (AE) of IP following docetaxel monotherapy was 14.3% (5/35 patients). Of the five patients who developed AE of IP, three patients died. The toxicity of this regimen was substantial, with treatment-related deaths occurring in 5 (14.3%) patients (AE of IP: 3, sepsis: 2). Docetaxel monotherapy has a poor activity and substantial risks when used for the treatment of platinum-resistant NSCLC with IP. Novel therapeutic approaches should be explored in this setting.