Animal Ordinances in Thornton, CO (2026)
7 verified animal ordinances for Thornton, Colorado, sourced directly from the municipal code and official government pages.
Verified from official government sources
Chickens & Livestock
Thornton allows up to six hen-only backyard chickens on detached-home lots in most residential districts, but bans roosters, most other livestock, and fowl citywide unless kept under the Agricultural or Residential Estate district rules or a miniature-goat permit.
Thornton Backyard Chicken and Livestock Rules
Some RestrictionsThornton City Code § 6-53
It shall be unlawful for any person to possess, harbor, keep, maintain, or permit backyard chickens in any area unless the following conditions and requirements are met: (1)Backyard chickens are permitted on lots developed with detached residential dwellings in the Residential - Low Density, Residential - Mid Density, Residential - High Density, Planned Development Legacy, Transit-Oriented Deve...
Dog Leash Laws
Thornton bans letting any domesticated animal run at large within city limits, and repeat offenses within a 12-month period trigger enhanced fines, impoundment, and a court-ordered dispositional hearing before the animal is released.
Thornton Leash Law and Animals-at-Large Rule
Some RestrictionsThornton City Code § 6-7
(a)It shall be unlawful for any owner of any domesticated animal to fail to prevent such animal from running at large within the city. It shall be an affirmative defense to this section that the animal was contained entirely upon private property with the consent of the person in lawful possession of such property.(b)It shall be unlawful for any owner of any domesticated animal to fail to preve...
Breed Restrictions
Thornton does not ban any dog breed by name. Instead it declares an animal 'aggressive' based on its actual conduct, such as biting or repeatedly lunging and snarling at people, and impounds and penalizes the animal regardless of breed.
Thornton Aggressive Animal Declaration Rule
Significant RestrictionsThornton City Code § 6-17
It shall be unlawful to possess any animal which engages in any of the following conduct within the city:(1)Inflicts a puncture wound, abrasion, or other wound upon a person or a domestic animal which injury does not meet the definition of bodily injury or serious bodily injury as defined in this chapter.(2)Without provocation, and without effective and immediate control, repeatedly snaps at or...
Beekeeping
Thornton requires a city beekeeping permit before keeping any hive, limits hive counts by lot size from two to eight hives, and mandates five-foot rear-yard setbacks plus flyway barriers near property lines.
Thornton Backyard Beekeeping Permit Rule
Significant RestrictionsThornton City Code §§ 6-102(a), 6-104(a)
No person shall keep, maintain or allow any hive of bees on any lot or parcel of land within the city without first obtaining a beekeeping permit in accordance with this article. This requirement does not apply to feral bees not managed by a beekeeper. ... It shall be unlawful to keep more than the following number of hives on any lot or tract within the city, based upon the size or configurati...
Exotic Pets
Thornton outright bans keeping wild animals within city limits, naming big cats, primates, bears, foxes, poisonous or long snakes, alligators, and wolf or coyote hybrids, and police can remove or destroy noncompliant animals.
Thornton Wild and Exotic Animal Ban
Heavy RestrictionsThornton City Code § 6-36(c)
Wild animals. It shall be unlawful for any wild animals to be kept or maintained within the corporate limits of the city. "Wild animal" shall be defined as any animal that customarily exists in its natural unconfined state and is usually not domesticated and shall include but not be limited to lions, tigers, cheetahs, panthers, cougars, mountain lions, ocelots, wildcats, bobcats, and other wild...
Pet Limits
Thornton caps most households at four dogs, four cats, or a combination totaling four, dropping to three dogs or three cats if a Vietnamese potbellied pig is also kept, with an exception for litters under three months old.
Thornton Household Pet Limit Rule
Some RestrictionsThornton City Code § 6-37(a)
It shall be unlawful for any person to harbor or allow there to be more than a total of four dogs, or four cats, or a combination of dogs and cats totaling no more than four, or one Vietnamese potbellied pig; provided, however, if dogs, cats, and pigs are harbored together only a total of three dogs or three cats along with one Vietnamese potbellied pig is allowed per residential dwelling unit ...
Mandatory Spay/Neuter
Thornton has no citywide mandatory spay/neuter law for all pets, but conviction for a habitually-at-large animal, an aggressive-animal violation, or an animal attack forces the owner to have the animal spayed or neutered and microchipped by court order.
Thornton Court-Ordered Spay/Neuter Penalty
Significant RestrictionsThornton City Code § 6-7(c)(2)
Any person who shall violate part (b) of this section shall, upon conviction, be subject to enhanced penalties as follows:a.Fined a sum of not less than $100.00 nor more than the maximum fine authorized by Section 1-8, or imprisoned for not more than one year, or both such fine and imprisonment; andb.Ordered to have the animal spayed or neutered by a licensed veterinarian or a licensed shelter;...
Looking for Adams County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Thornton city rules.
Animal Ordinances in Adams County →