Young puppies and kittens have unique physiologic needs in regards to fluid therapy, which must address hydration, vascular fluid volume, electrolyte disturbances, or hypoglycemia. Pediatric patients have a higher fluid requirement compared with adults and can rapidly progress from mild dehydration to hypovolemia. Simultaneously, their small size makes overhydration a real possibility. Patient size complicates fluid administration because catheters used in larger pets may be difficult to place. Routes of fluid administration used in the neonate or pediatric patient include oral, subcutaneous, intraperitoneal, intraosseous, and intravenous. Clinicians should be aware of the pros and cons of each route.