Rationale: Immune checkpoint inhibitors (ICIs) are the mainstay of treatment for various metastatic tumors. Pneumonitis is a potentially fatal side effect of ICIs. However, there is little data regarding risk factors for developing ICI pneumonitis (ICI-p). Here, we evaluate whether findings on pre-treatment PFTs are associated with the development of ICI-p. Methods: We conducted a retrospective cohort study of patients who received at least one dose of ICI from 2011 to 2017 at The Ohio State University. Pneumonitis cases were determined by the treating oncologist and retrospectively evaluated for agreement between an oncologist and pulmonologist. Pneumonitis severity was assigned based on the CTCAE v4. The following potential risk factors for ICI-p were recorded among patients with PFTs and chest imaging within 18 months of ICI treatment: age, sex, ICI type, cancer type, line of therapy, performance status (PS), smoking history and COPD history. These were compared between patients with and without pneumonitis, and between patients with severe (grade 3-5) and mild (grade 1-2) pneumonitis using Kruskal-Wallis test for continuous variables and fisher’s exact test for categorical variables. Results: 1,097 patients received ICI between 2011 and 2017 and 46 developed ICI-p. Only 115 (10.5%) had spirometry (FEV1, FVC), 92 (8.4%) had lung volume (TLC) testing, and 102 (9.3%) had diffusion capacity (DLCO) assessment within 18 months of ICI treatment. Patients with non-small cell lung cancer (NSCLC) were more likely to have undergone recent PFTs than other cancers: NSCLC patients represented 24.15 % compared to 7.3% (p<0.001). Among patients with recent PFTs, FEV1 and FVC were not associated with development of ICI-p (p-values>0.05), but TLC < 80% predicted and DLCO corrected for hemoglobin < 80% predicted was associated with increased risk of pneumonitis (31.8% vs 11.4%, p=0.043; 28.9% vs 9.4%, p=0.018, respectively). Low TLC and low DLCO were not associated with development of severe (vs mild) pneumonitis. There was no significant difference in survival in patients with or without ICI-p (p=0.33). Conclusions: The incidence of ICI-p was associated with low TLC and low DLCO on pre-treatment PFTs. However, these were not associated with severity of ICI-p. A low percentage of patients undergo pre-treatment PFTs for ICIs and patients with lung cancer were more likely to have PFTs before ICI. Future studies will need to determine the predictive value of PFTs for ICI-p.