BACKGROUND The appearance of the intestinal mucosa during endoscopy varies among patients with primary intestinal lymphangiectasia (PIL). OBJECTIVE To classify the endoscopic features of the intestinal mucosa in PIL under endoscopy, combine the patients' imaging and pathological characteristics of the patients, and explain their causes. METHODS We retrospectively analyzed the endoscopic images of 123 patients with PIL who were treated at the hospital between January 1, 2007 and December 31, 2018. We compared and analyzed all endoscopic images, classified them into four types according to the endoscopic features of the intestinal mucosa, and analyzed the post-lymphographic computed tomography (PLCT) and pathological characteristics of each type. RESULTS According to the endoscopic features of PIL in 123 patients observed during endoscopy, they were classified into four types: nodular-type, granular-type, vesicular-type, and edematous-type. PLCT showed diffuse thickening of the small intestinal wall, and no contrast agent was seen in the small intestinal wall and mesentery in the patients with nodular and granular types. Contrast agent was scattered in the small intestinal wall and mesentery in the patients with vesicular and edematous types. Analysis of the small intestinal mucosal pathology revealed that nodular-type and granular-type lymphangiectasia involved the small intestine mucosa in four layers, whereas ectasia of the vesicular- and edematous-type lymphatic vessels largely involved the lamina propria mucosae, submucosae, and muscular layers. CONCLUSIONS Endoscopic classification, combined with the patients' clinical manifestations and pathological examination results, is significant and very useful to clinicians when scoping patients with suspected PIL.