Background: Proton pump inhibitors (PPIs) are known to be beneficial in symptomatic control of gastroesophageal reflux disease and gastritis which can be a common complication of various cancers specifically gastrointestinal (GI) cancers. Microscopic colitis development has been studied to be associated with PPI use. Immune checkpoint Inhibitor (ICI) colitis is a known adverse effect of Inhibitors of Programmed cell death 1 (PD-1) and its ligand (PD-L1). Previous studies have also shown use of PPIs and NSAIDs are common risk factors which can exacerbate ICI Colitis caused by Inhibitors of PD-1 and PD-L1. This study is designed to observe association of certain drugs especially PPIs in ICI colitis. Methods: This is a single center, retrospective, and observational study that investigated patients treated with PD-1 and PD-L1 Inhibitors for management of any type of cancer between January 2022- September 2023. A list of patients treated with PD-1 and PD-L1 inhibitors was obtained from Inpatient pharmacy records followed by retrospective chart review to look for symptoms of colitis and other medications used by each patient. Primary outcome was to observe the role of PPIs in ICI colitis. Secondary outcomes were to observe the number of patients with GI cancers on PPIs who developed colitis. We also observed the effect of NSAIDs use as a potential risk factor in the population with ICI colitis. Results: The data consisted of 93 patients of which 17 (18.3%) developed colitis. Among this population 13 (76.5%) was ICI colitis, 2 (11.7%) was diverticular colitis and 2 (11.7%) was Infectious colitis. PPI use was seen in 3 out of 13 patients (23%) with ICI colitis. Patients with any type of GI cancer who developed colitis was 5 (25%) and PPI use in ICI colitis was seen in 2 out of these 5 patients. NSAIDs use was seen in 3 (23%) patients with ICI colitis. Conclusions: We did not observe significant association between PPI use and ICI colitis. ICI use becoming increasingly common in oncologic population, larger studies may be needed to further evaluate risk factors associated with ICI colitis in this population.