Longmont Small Animal Hospital Share: Veterinarians Longmont Small Animal Hospital Visit Website Request Info 20 3rd Ave. Longmont, CO 80501 303-651-3039 303-651-7691 (fax) www.longmontsmallanimalhospital.com About Map About Welcome to Longmont Small Animal Hospital. We are a full service small animal hospital providing comprehensive healthcare services to pets in Longmont and the surrounding areas. What's Nearby? Distance: 5 10 15 20 25 50 mi.