Animal hoarders pathologically accumulate more animals than they can properly care for. This study compared long-term outcomes for 371 cats that were surrendered to a high-quality private shelter from 14 hoarding environments. Various illnesses related to overcrowding, including upper respiratory infection, skin disease (eg, inflammation, alopecia, wounds), fleas, ear mites, and gingivitis, were common. Upper respiratory infection was significantly more prevalent in cats from institutional hoarding environments (ie, organizations advertising themselves as rescues or shelters). In 11 of the 14 hoarded groups, ≥90% of the cats were eventually adopted. The authors attributed this high success rate to manageable group sizes and managed intake, generous funding, and collaboration with community members.