Abstract The morphological characteristics of the endocrine pancreas of nutria in female and male nutria at the age of 1 day, 2 months, 4.5 months, 7.5 months and 12 months have a number of sex and age characteristics and differences. The number of islets in pancreatic lobules at 1 day of age in males is 3–6, and in females – 2–3. At 2 months of age, their number in males decreases to 2–4, and in females it increases to 5–6. From 4.5 months of age, the number of islands in females and males ranges from 2 to 3. At 1 day and 2 months of age, in nutria, islet division is recorded due to the cleavage and formation of new cell groups. The area of endocrine islets in females and males of nutria changes in a wave-like manner with age, having minimum values in 1-day and 4.5 months of age, and the maximum at 12 months of age. The nuclear-cytoplasmic ratio of endocrine islet insulocytes in nutria increases from 1 day to 2 months of life to their maximum values, and in subsequent age periods decrease and by the age of 12 months reaches its minimum.