Background: Mutations in the epidermal growth factor receptor (EGFR) gene have been identified in 10%–50% of patients with non-small cell lung cancer (NSCLC). Exon 20 insertion mutations represent about 2%–10% of this group. Reports of real world experience of NSCLC patients with EGFR exon 20 insertion mutations are limited. This study describes patient characteristics, treatment patterns, and survival outcomes of NSCLC patients with EGFR exon 20 insertions based on real world data. Methods: Flatiron Health electronic health record data, largely from community oncology practices, from January 2011–April 2018 were used for this retrospective observational study. Treatment-naïve (TN) and relapsed/refractory (RR) second-line patients diagnosed with NSCLC with EGFR exon 20 insertion mutation aged ≥18 years at treatment initiation were included. Patient characteristics were described, and Kaplan-Meier analyses were used to assess real world overall survival (rwOS) separately for TN (starting at first-line therapy) and RR (starting at second-line therapy) patients. Results: There were 128 TN and 71 RR patients identified. Median age was 66.5 and 65.0 years for TN and RR patients, respectively, and over half were female (TN: 59.4%, RR: 53.5%). Among 83 TN and 47 RR patients with known ECOG score at advanced diagnosis, most had score 0–1 (TN: 56.3%; RR: 62.0%). Central nervous system metastases were observed in 35.2% of TN and 33.8% of RR patients. While 45.3% of TN patients received any chemotherapy, approximately 20% of both TN and RR patient groups had exposure to various EGFR TKIs. Overall, median rwOS was low at 14.6 months for TN patients, and 10.1 months for RR patients. Conclusion: Real world survival of patients with EGFR exon 20 NSCLC remains poor. Treatment with any chemotherapy regimen was most commonly used followed by EGFR TKIs in TN patients, while the proportion treated with chemotherapy and EGFR TKIs was similar in RR patients. Despite limited evidence in this population, over a fifth of TN and RR patients received EGFR TKI monotherapy. This study demonstrated unmet need for improved therapeutic options in TN and RR patients with NSCLC with EGFR exon 20 insertion mutation.