“Postprandial fullness” is one of the symptoms of dyspepsia and is primarily associated with food intake. Therefore, the Rome IV criteria, which are the diagnostic criteria for functional dyspepsia (FD), identify “bothersome postprandial fullness” as one of the characteristic symptoms of the postprandial distress syndrome subtype of FD. In the management of patients with chronic postprandial fullness, it is important to carefully differentiate possible underlying diseases. Consider the differential diagnosis of systemic diseases such as collagen diseases, endocrine disorders, metabolic diseases, drug-induced causes, and organic gastrointestinal diseases. FD can only be diagnosed after these diseases have been ruled out. The pathophysiology of postprandial fullness involves multiple factors, and the mechanisms by which symptoms arise are complex. For example, delayed gastric emptying and impaired gastric accommodation are considered representative mechanisms. The first-line treatments for FD are acotiamide, gastric acid-secretion inhibitors (proton pump inhibitors and histamine H2 receptor antagonists), and Rikkunshito (a Kampo medicine). Acotiamide is a prokinetic agent and improves gastric emptying and gastric accommodation through acetylcholinesterase inhibition.