Background: Phlegmonous gastritis is a rare condition caused by bacterial infection of the gastric wall. Largely regarded as an acute process with poor prognosis, published reports describe a wide variation in its clinical presentation. In this study, we describe five cases of phlegmonous gastritis seen at a single large academic referral center that demonstrates an association with immunosuppression and gastric stasis. Case Presentation: Two Caucasian females and three Caucasian males, ages 35 to 78 years, were identified with histologic and/or endoscopic characteristics of phlegmonous gastritis. Abdominal pain, nausea, and vomiting were the most common presenting symptoms. Two patients underwent outpatient evaluation, while the three other patients required hospital admission. On endoscopy, superficial gastric ulcerations, mucosal friability, and diffuse exudate were noted. Endoscopic biopsies showed evidence of severe active and suppurative gastritis. At diagnosis, three patients were immunosuppressed whose comorbidities included rheumatoid arthritis on abatacept, amyloidosis status-post stem cell transplantation, and Crohn’s disease on leflunomide therapy. The remaining two patients had evidence of gastric stasis due to gastroparesis and gastric outlet obstruction respectively. In all cases, symptomatic resolution was achieved with medical management including broad-spectrum antibiotics and proton pump inhibitor. Conclusion: The rarity of phlegmonous gastritis and its diverse presentation represent a diagnostic challenge. Improved recognition of the factors, such as immunosuppression, which predispose to this condition is crucial for timely management and may provide further insight to understanding its pathophysiologic mechanisms. Our case series further demonstrates that gastric stasis and inflammatory bowel disease may be under-recognized risk factors and should be areas of future study.