Background: Apelin is a recently discovered peptide, identified as an endogenous ligand of receptor APJ, apelin has beneficial effect in diabetic conditions as it increase glucose uptake and improve insulin sensitivity, diabetic patients have impaired gastric secretion and apelin is expressed in parietal, chief and mucous cells and this raise the possibility of involvement of apelin in gastric physiology. Objective: The present study was carried out to demonstrate the effect of acute and chronic administration of apelin 13 on gastric secretion in normal and diabetic rats. Design: 98 adult wistar male albino rats were used, animals were divided into three main groups group A (normal rats), group B (high fat diet induced diabetic rats) and group C (streptozotocin induced diabetic rats), each group is subdivided into control subgroup (1), acute apelin-13 injected subgroup (2), chronic apelin-13 injected subgroup for 21 days (3): In all studied groups, different parameters of gastric secretion, gastric mucosal pH and mucin content were measured. Results: acute administration of apelin-13 decreased gastric acid secretion in all groups proved by significant increase in pH accompanied by significant decrease in total and free acidity, the percentage in decrease of gastric acid secretion in normal rats is more than that of high fat diet induced diabetic rats and streptozotocin induced diabetic rats. Ghrelin level, volume of gastric secretion, blood glucose and HOMA- IR significantly decreased in all groups. pepsin, mucin content of gastric mucosa and insulin level had no significant change in all groups, while, pH of gastric mucosal surface significantly increased .In addition, there was negative correlation between ghrelin level and pH, positive correlation between ghrelin and both total and free acidity in normal rats, positive correlation between ghrelin and volume of gastric secretion in all studied groups. Chronic administration of apelin-13 caused no change in gastric acidity in normal rats. and increase gastric acidity in high fat diet induced diabetic rats and streptozotocin induced diabetic rats, proved by significant decrease in pH accompanied by significant increase in total and free acidity, the percentage of increase in gastric acid secretion in high fat diet induced diabetic rats is more than that of streptozotocin induced diabetic rats, moreover, chronic administration of apelin-13decreased ghrelin level, pepsin level, volume of gastric secretion, blood glucose, insulin level and HOMA- IR and increase pH of gastric mucosal surface and mucin level in all studied groups. In addition, there is positive correlation between ghrelin and volume of gastric secretion in all studied groups. Conclusion: While apelin-13 injection on chronic run caused no change in gastric acidity in normal rats, it improved gastric acidity in diabetic rats and can act as a promising target for type 2 diabetes treatment. In addition apelin-13 can be considered as gastro protective agent as it increased pH of gastric mucosal surface and mucin level in normal and diabetic rats.