We evaluated the safety and efficacy of gefitinib treatment in elderly patients with non-small-cell lung cancer (NSCLC). We retrospectively compared toxicity, response and survival outcomes for gefitinib in patients aged 75 years or older (elderly group) with the same outcomes in patients aged younger than 75 years. In total, 350 patients were eligible for this analysis, of whom 92 were in the elderly group and 258 in the non-elderly group. In the elderly group, adverse events were generally mild to moderate and grade 3-4 adverse events were observed in 8 (9%) patients. The objective response rate (17 vs. 21% for elderly vs. non-elderly, respectively) and median survival time (7.6 vs. 9.3 months) were also similar in the two groups. Multivariate analysis revealed elderly patients with lower Brinkman index tended to be more sensitive to gefitinib (odds ratio: 4.57, 95% confidence interval: 0.91-22.72, p = 0.0642). In this study, treatment with gefitinib appeared to be as safe and effective in elderly patients (aged 75 or older) with NSCLC as in non-elderly patients.