The term diabetes mellitus, referred to in this chapter as diabetes, is a complex disorder of carbohydrate metabolism characterized by hyperglycemia that results from defects in insulin secretion and/or insulin action leading to consequences from glucose intolerance. The etiology of diabetes in the pediatric age group can be quite varied. This chapter will focus on the more common presentations of diabetes in the pediatric age group; Type 1 diabetes mellitus (T1D), Type 2 diabetes mellitus (T2D), monogenic diabetes (MODY and neonatal diabetes) with a brief mention of other etiologies of diabetes mellitus seen in the pediatric population. Nutritional consideration in management of diabetes involves thoughtful consideration of carbohydrate intake complementing medical management, while balancing protein and fat intake to promote growth and energy requirements of the child.