Betatrophin [also known as lipasin, angiopoietin‑like 8 (ANGPTL8), refeeding induced in fat and liver (RIFL), or hepatocellular carcinoma‑associated gene TD26], a 22‑kDa protein in the angiopoietin‑like family, is a liver‑derived hormone that promotes pancreatic β‑cell proliferation and lipid metabolism. The aim of the present study was to investigate the effect of recombinant betatrophin on β‑cell regeneration in a neonatal streptozotocin (STZ)‑induced diabetic rat model. One‑day‑old Wistar rats were injected with STZ (100 mg/kg), followed by intraperitoneal administration of betatrophin to the STZ‑injected rats for 6 days. Plasma glucose and body weight were monitored. On days 4 and 7, expression levels of pancreatic duodenal homeobox gene‑1 (PDX‑1), the Bax/B‑cell lymphoma‑2 (Bcl‑2) ratio and plasma insulin were assessed, and the β‑cell proliferation rate was determined. Pancreatic islet area and number were determined at 10 weeks. It was found that betatrophin treatment alleviated STZ‑induced hyperglycemia, elevated pancreatic expression levels of Bcl‑2, PDX‑1, plasma insulin levels and the β‑cell proliferation rate on days 4 and 7. Long‑term betatrophin treatment improved glucose tolerance, associated with improved plasma insulin levels and β‑cell mass. These results suggest that early administration of betatrophin promotes β‑cell proliferation in STZ‑induced diabetic neonates and prevents the development of diabetes in adults.