Pancreatic β cells produce insulin and play a central role in glucose homeostasis. The regenerative capacity of mammalian β cells is limited, so that loss and dysfunction of β cells causes diabetes. Zebrafish have a pancreas which is functionally and morphologically conserved with human pancreas. Zebrafish have high regenerative capacity of islets. In the present review, development of zebrafish pancreas was described in comparison to that of mammals, and the regenerative process of zebrafish pancreas was also described. This review will give information on understanding islet and pancreatic β cell development and regeneration and provide possibilities of zebrafish research for developing new diabetic therapies and regenerative medicines.