Background: Immune-checkpoint inhibitors (ICIs) have revolutionized lung cancer therapy. The data on the use of ICIs in underrepresented populations with lung cancer (older patients, patients with autoimmune disease (ADs), and patients with poor performance status) are limited from trials. The real-world pattern of immune-related adverse effects (irAEs) and the association between the occurrence of irAEs and prognosis remain unclear. Methods: Patients with lung cancer newly started on ICIs from 10/01/2018 to 09/30/2021 were identified in the Tufts Medical Center cancer registry. Patient information, disease characteristics, treatment history, and outcomes were collected from the electronic health record. Time to ICI treatment initiation (TTI) was analyzed via log-rank tests. Multivariable Cox regression was used to assess the impact of the occurrence of irAEs on overall survival (OS). Results: 125 lung cancer patients were identified with a median age of 70 (range 50-80) years old at time of ICIs initiation. 68 (54.4%) were males and 103 (82.4%) were White. Most of the patients were past or current smokers (95.2%). 16 (12.8%) had a history of ADs and 44 (35.2%) had an ECOG status >1. Most of the cohort had non-small cell lung cancer (80.8%) and advanced-stage diseases (stage III 20.8%, stage IV 77.6%). 37.6% had PD-L1 expression and 25.6% had detected molecular alterations. ICIs were mostly used in frontline settings (65.6%) and for palliative intent (86.4%). Pembrolizumab was used most frequently (64%), followed by durvalumab, atezolizumab, nivolumab, and ipilimumab plus nivolumab. About half (49.6%) of ICIs were delivered concurrently with chemotherapy. A total of 50 irAEs occurred in 39 (31.2%) individuals. The most common irAEs were pneumonitis, thyroid disorders, dermatitis, and gastrointestinal toxicity. TTIs were similar comparing those ≥65 vs <65 years old (median TTI: 1.4m vs 1.17m, p=0.82), those with vs without ADs (median TTI: 1.53m vs 1.27m, p=0.53), and those with ECOG >1 vs ≤1 (median TTI: 1.6m vs 1.17m, p=0.06) in newly diagnosed stage IV lung cancer patients (N=62). After adjusting for age, BMI, stage, histology, performance status, and comorbidities, no differences were found in OS between those with irAEs and those without (HR=0.84, p=0.65). Conclusions: Our findings suggested that in the real world, older patients, patients with ADs, and patients with poor performance had no significant delays in ICIs initiation. The pattern of irAEs was similar to that reported in clinical trials without erosion of OS among those with irAEs.