Background The long-term impact of COVID-19 on cancer patients receiving immune checkpoint inhibitors (ICIs) remained unknown. This study aimed to investigate the association between COVID-19 and long-term outcomes in ICIs-treated lung cancer patients. Methods Three hundred eighty-one patients with advanced lung cancer who were treated with ICIs were enrolled and followed for at least 6 months in 10 medical centers in China during Omicron pandemic. The primary endpoints were overall survival (OS) and progression-free survival (PFS). Cox model with time-dependent covariate and landmark analysis were used. Results The multivariable analysis showed that patients with COVID-19 had significantly worse OS (HR: 2.59 [1.58–4.26], P < 0.001) and PFS (HR: 1.55 [1.02–2.35], P < 0.001). In landmark analyses, COVID-19 that occurred within 3 months after initiation of ICIs was found to be associated with shorter OS (HR: 3.40 [1.70–6.77], P = 0.001) and PFS (HR: 3.40 [1.70–6.77], P = 0.02). In subgroup analysis, both mild and severe COVID-19 were associated with shorter OS (mild, HR: 2.39 [1.33–4.29], P = 0.004; severe, HR 4.46 [2.39–8.33], P < 0.002) and PFS (mild, HR 1.71 [1.05–2.78], P = 0.03; severe, HR 3.32 [1.97–5.60], P < 0.002). Additionally, there were no significant differences in OS or PFS among patients with varying treatment delays. Conclusions COVID-19 had a negative impact on the long-term outcomes of patients with lung cancer who received ICIs, particularly if the infection occurred during the first 3 months of ICIs treatment. These findings are crucial for addressing the COVID-19 epidemic and other respiratory infectious diseases.