Background: It is unclear whether there is a difference in the efficacy of treatment by epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) between patients with postoperative recurrent non-small-cell lung cancer (NSCLC) and those with stage IV NSCLC harboring EGFR mutations. Patients and Methods: The records of NSCLC patients harboring EGFR mutations who were treated with gefitinib or erlotinib were retrospectively reviewed, and the treatment outcomes were evaluated. Moreover, we performed an immunohistochemical analysis of PD-L1 expression in tumor lesions of the postoperative recurrence group. Results: In 205 patients, both the progression-free survival (PFS) time (9.4 vs. 16.9 months) and the median survival time (24.7 vs. 37.4 months) were significantly longer in the postoperative group than in the stage IV group. Additionally, multivariate analysis identified that postoperative recurrence was an independent predictor of PFS and overall survival, as were performance status and smoking status. The PFS durations were 15.7 and 16.6 months for the high- and low-PD-L1 expression groups, respectively, and no significant difference was observed (P = 0.73). Conclusions: The findings of this study provide a valuable rationale for considering postoperative recurrence as a predictive factor for favorable PFS and overall survival in patients with NSCLC harboring activating EGFR mutations who receive EGFR-TKIs.