Introduction Erlotinib is an effective treatment option for EGFR-mutant non-small cell lung cancer. It is important to predict patients who will respond better to erlotinib. We designed this study to investigate the effect of renal insufficiency (RI) on erlotinib treatment outcomes. Methods All patients receiving erlotinib were stratified into 3 groups. Group 1 consisted of non-RI subjects with classical epidermal growth factor receptor (EGFR) mutations, Group 2 consisted of those with RI (Estimated glomerular filtration rate <60 mL/min) and classical EGFR mutations, and Group 3 consisted of those with non-classical EGFR mutations. Results 82 patients were included in the study. Median progression-free survival (PFS) in patients with classical mutation was approximately 6 months shorter in those with RI, although not statistically significant. Median overall survival (OS) in Group 1, 2 and 3 was 34.1 months, 35.2 months, and 15 months, respectively and although not statistically significant, median OS was 20 months shorter in Group 3. Univariate and multivariate cox-regression analysis revealed shorter PFS and OS in males and those with ECOG >= 2 while PFS and OS were longer in those with recurrent lung tumors and generating rash during erlotinib treatment. There was no difference between RI and non-RI patients in terms of adverse events except for fatigue and appetite loss. Conclusions This research showed OS in patients with and without RI was comparable. Although not statistically significant, PFS in patients with classical mutation was approximately 6 months shorter in those with RI patients.