Background: The Covid-19 pandemic directly affected the screening, diagnosis, and treatment of lung cancer patients. Our group recently reported that the rate of new lung cancer diagnoses declined during the first year and significantly increased during the second of COVID-19 pandemic. The effect of COVID-19 on lung cancer treatment outcomes in literature is still limited and mostly reported either as predictive survival using prioritization and modeling techniques. In this study, we aimed to quantify the effect of COVID-19 on lung cancer survival using real world data collected at the Jewish General Hospital, Montreal. Methods: This is a retrospective chart review study including patients diagnosed with lung cancer between March 2019 and March 2022. We compared 3 cohorts: Cohort1: 2019 (pre-COVID) Cohort2: 2020 (1^st year of COVID) Cohort3: 2021 (2^nd year of COVID). Results: A total of 417 patients were diagnosed and treated with lung cancer at our centre throughout the three-year study: 130 in 2019, 103 in 2020 and 184 in 2021. Although the proportion of advanced/metastatic stage lung cancer remained the same for the three cohorts, there was a significant increase in the late-stage presentation during the pandemic. The proportion of M1c (multiple extrathoracic sites) cases in Cohorts 2 and 3 was 57% and 51% respectively compared to 31% in cohort 1 (p < 0.05). Median survival for early and locally advanced stages of lung cancer was similar in the 3 cohorts. However, the subgroup of patients diagnosed in the advanced/metastatic stage had a significantly increased risk of death during the pandemic (cohorts 2 and 3). The 6-month mortality rate was 53% in 2021 compared to 47% in 2020 and 29% in 2019 (p = 0.004). The median survival in this subgroup of patients decreased significantly from 13 months in 2019 to 6 months in 2020 and 5 months in 2021 (Table 1). Conclusions: The present study represents the impacts of the COVID-19 on lung cancer survival outcome. The COVID-19 pandemic potentially caused the significant shift to M1c stage and contributed to an increase 6 month mortality rate and poorer overall survival in the advanced/metastatic lung cancer patients diagnosed and treated during the pandemic.