Gastric syphilis is a rare manifestation of syphilis that occurs in about 1% of cases and is often overlooked due to its non-specific signs and symptoms. We report a case of a 28-year-old Chinese woman who presented with epigastric pain, nausea, vomiting, hematemesis, alopecia, and weight loss. She tested positive for Helicobacter pylori (H. pylori), with rapid plasma reagin (RPR) and Treponema pallidum particle assay (TPPA) tests showing titers of 1:128 and 1:320, respectively. CT imaging revealed thickening of the gastric wall, exudation around the antrum, and multiple lymphadenopathies. Gastroscopy showed multiple irregular ulcers, which resembled lymphoma. However, biopsy results did not support the presence of lymphoma, but immunohistochemistry showed an abundance of syphilis spirochetes in the mucosal lamina propria and glands. This led to a diagnosis of gastric syphilis. The patient received standard treatment for syphilis as well as anti-H. pylori therapy, and her symptoms and endoscopic findings gradually improved and eventually resolved. We hope that this case report can provide valuable insights into the diagnosis and management of gastric syphilis, which can mimic other diseases like lymphoma.