Differently from epidermal growth factor receptor (EGFR) 19Del and L858R mutations, the panoramic description of uncommon EGFR mutations is far from mature. Our understanding of its population characteristics, treatment response, and drug resistance mechanisms needs urgent expansion and deepening. Our study enrolled 437 patients with non-small-cell lung cancer from four clinical centers and who had uncommon EGFR mutations. The clinical characteristics of all patients and the treatment outcomes of 190 advanced patients who received pharmacotherapy were analyzed. Moreover, the acquired resistance mechanisms were explored based on 53 tissue or liquid re-biopsy data in 45 patients. Patients with EGFR 20ins had a shorter survival time compared with patients with non-20ins mutations. In total, 149 cases had received EGFR-tyrosine kinase inhibitors (TKI); afatinib was significantly superior to other EGFR-TKIs both in ORR and mPFS in all uncommon mutations and especially in the L861Q group. The most common acquired drug resistance mechanism was MET amplification, followed by EGFR T790M, which was significantly different from common EGFR mutations.