An open admission, no-kill, private animal shelter in the Northeastern United States housing approximately 250 cats experienced an outbreak of sudden death, vomiting, and diarrhea in their feline population in four distinct areas within the shelter. Two weeks into the outbreak, a volunteer spay/neuter community veterinarian diagnosed feline panleukopenia in multiple cats via canine parvovirus ELISA SNAP test. Over the course of one month, 40-45 cats of all ages either died or were euthanized as a result of their disease. At this point, Maddie’s Shelter Medicine Program at Cornell University was invited to the shelter for a consultation regarding management of the outbreak. Field investigation of the shelter facilities and assessment of standard operating procedures determined that the main factor contributing to the outbreak was inadequate vaccination. Inappropriate housing, overcrowding, and prolonged length-of-stay also promoted a high-stress environment conducive to the rapid spread of feline panleukopenia. Recommendations made to manage the outbreak included consistently vaccinating all cats with a modified live FVRCP vaccine on intake, establishing a designated isolation area, quarantining exposed cats, discouraging intake of new animals, separating incoming cats from the general population, decreasing length-of-stay, and euthanizing symptomatic kittens. After implementation of a new quarantine system and improved vaccination protocols, no new cases of panleukopenia developed. Most of the remaining kittens survived, and even though the shelter admitted two panleukopenia positive kittens, they did not experience another outbreak. This case discussion will serve to highlight basic principles of herd health and population management applied to companion animals in shelter medicine.