Immune checkpoint inhibitors (ICIs) elicit antitumour effects by activating the host immunity and cause immune-related adverse events (irAEs). ICI-related interstitial lung disease (ICI-ILD) is a fatal irAE that is difficult to treat; moreover, its incidence is relatively higher in patients with lung cancer. Therefore, early ICI-ILD detection and intervention are important for patient safety. However, a risk assessment method for ICI-ILD has not been established and the prediction of ICI-ILD occurrence is difficult. The aim of our study was to identify the risk factors associated with ICI-ILD. To this end, we retrospectively analysed 102 patients with lung cancer who first received ICI and completed the treatment between April 2016 and December 2019 at Tokushima University Hospital. Nineteen patients had all grades of ICI-ILD and 10 had grade ≥ 3 ICI-ILD. The 30-day mortality rate of patients with grade ≥ 3 ICI-ILD was the highest among all patients (P < 0.01). The multivariate logistic analysis indicated that the performance status ≥ 2 alone and both performance status ≥ 2 and ≥ 50 pack-year were independent risk factors of ICI-ILD of grade ≥ 3 and all grades, respectively. Overall, our study provides insights to predict ICI-ILD occurrence.