AbstractImmune‐related adverse events (IrAEs) of immune checkpoint inhibitors (ICIs) can be serious and unpredictable. We examine the incidence rate and risk factors for IrAEs in an Asian cohort of nonsmall cell lung cancer (NSCLC) patients treated with immunotherapy. Between June 2014 and August 2020, we retrospectively analysed IrAEs in NSCLC patients treated with anti‐PD‐1 or anti‐PD‐L1 inhibitors at the National University Cancer Institute, Singapore. A Poisson regression model was used to estimate the effect of risk factors on incidence rate of any grade IrAEs. One hundred and forty‐one patients were enrolled. Median age was 63. Majority were male (67%) with Eastern Cooperative Oncology Group (ECOG) PS 0‐1 (77%). More than half (56%) received pembrolizumab. Eleven percent harboured epidermal growth factor receptor (EGFR) mutation. Eighteen percent received concomitant chemotherapy. Median number of cycles was 4, and median duration of treatment was 2.1 months. IrAEs were seen in 71 (50.4%) patients, with an incidence rate of 99 events per 1000 person‐months. Fatigue (25%), rash (10.5%) and pneumonitis (7.9%) were the most common IrAEs. Twenty out of 152 IrAEs (13.2%) were Grade 3 or higher in severity: most common being pneumonitis (5.3%), fatigue (3.3%) and transaminitis (1.3%). Multivariable analysis demonstrated that concomitant chemotherapy use, higher BMI and presence of EGFR mutation are significant predictors for IrAEs (P < .0001; P = .016; P = .007). Our findings can help guide risk stratification and monitoring of IrAEs among NSCLC patients on immunotherapy.