Background & Aims: Amyloidosis is a group of systemic disorders caused by extracellular deposition of misfolded serum proteins. Gastrointestinal (GI) involvement is associated with a higher risk of GI bleeding, especially if mucosal lesions are present. Our study aims to evaluate the frequency of GI manifestations in patients with amyloidosis, to clinically characterize these patients and to describe the endoscopic and histopathologic findings in GI amyloidosis. Methods: A retrospective, single-center study of all patients admitted with amyloidosis and GI manifestations was conducted at a German University Hospital between July 2003 and June 2023. Clinical, endoscopic, and histopathological data was retrieved from medical records. Results: Between July 2003 and June 2023, 63 patients with different types of amyloidosis were included into the study. Twenty-three (36,5%) were diagnosed with GI involvement of amyloidosis (60.9% male, median age 62 +/- 18.28 years). The distribution of the types of amyloidosis were amyloid light chain (AL) at 52.5%, transthyretin (ATTR) at 21.7%, amyloid A (AA) at 13.0%, and unknown at 18%. Initial GI symptoms were present in 78.3% of the patients and included mainly diarrhea (34.8%), and abdominal pain (30.4%) Affected GI organs were primarily the colon (60,8%) and the stomach (39.1%). Endoscopic findings were ulcerations (47.8%), mucosal inflammation (43.5%), polyps (26.1%), erosions (13.0%), vascular malformation, polypoid protrusion, submucosal hematoma, erythema, metaplasia, and diverticulum. Histopathological findings included vascular wall thickening, (peri-)vascular and interstitial amyloid deposition. Gastrointestinal bleeding occurred in 39.1% of the patients. The mortality rate 5 years after diagnosis was 47.8%. Conclusions: Gastrointestinal amyloidosis can present with multiple symptoms and endoscopic findings, rendering diagnosis a challenge. Of clinical relevance, GI bleeding was a frequent event in our patient cohort. Therefore, clinicians must be aware of GI bleeding as a manifestation of amyloidosis and definite diagnosis should be achieved based on biopsy results.