Crossing the Border with a Pet
Crossing the border with a pet used to be one of the easier things about cross-border life. That is no longer true for dogs, and the reason is a parasite rather than rabies. The United States classified Mexico as affected by the New World screwworm in November 2024 and started requiring a certificate on dogs coming north. Mexico then detected the screwworm inside the United States and started requiring one on dogs going south. Cats are exempt going south. Coming north, the 2 authorities that would know do not agree about cats, and this guide says so rather than guessing.
This is an overview, not legal advice. These rules moved twice in 2 years, so confirm the current requirements with APHIS, the CDC, and SENASICA before a trip that matters.
The 5 day clock, which is the whole problem
Here is the part to plan around, because everything else is paperwork you can do once.
A dog crossing south needs a screwworm certificate signed by a USDA-accredited vet in the United States. A dog crossing north needs a different screwworm certificate signed by an authorized vet in Mexico. Each one is valid for 5 days. There is no version of either that covers the round trip, and no version that lasts a month.
So a dog that goes down for a weekend needs 2 certificates from 2 veterinarians in 2 countries, and both clocks are short enough that you cannot get ahead of them. Find your vet on each side before you plan the trip, not the morning of. The CDC form below is the easy one: fill it out once and it lasts 6 months.
Going into Mexico
Mexico dropped its general pet health certificate requirement years ago, and for cats that is still true. A cat goes south with no certificate at all.
For dogs, that changed on August 3, 2026. A pet dog traveling from the United States into Mexico now has to arrive with an NWS Inspection Certificate for Pet Dogs, issued and signed by a USDA-accredited veterinarian no more than 5 days before you arrive. The form is a screwworm inspection specifically, not a general health certificate, and it does not need APHIS endorsement, so your accredited vet can sign it and hand it to you the same day. The 5-day window is the part that bites: it is not a document you get once and keep.
Dog or cat, you then report to the Agricultural and Livestock Health Inspection Office, the OISA, at the port for a visual inspection by SENASICA. The officer checks that your pet shows no sign of infectious disease, is free of ectoparasites, and has no fresh or healing wounds. Bring the animal in a clean carrier and carry only the day's portion of food. If the carrier arrives dirty or holds disposable bedding, toys, or food items, those get removed for disposal. If ticks turn up, SENASICA takes a sample for the official laboratory and the pet can be held at the OISA until the lab clears it, with any resulting costs on you.
SENASICA also runs a Frequent Traveler Pet Program that regular crossers can register for. It does not waive the certificate or the inspection, and we have not verified what it does change, so treat it as something to ask about at the OISA rather than as a shortcut.
Ferrets cannot be brought into Mexico from the United States at all right now, and pet birds run on a separate and heavier process. This guide covers dogs and cats.
Coming back into the United States
Going north, 2 separate federal agencies want 2 separate things from a dog, and satisfying one does not satisfy the other.
The CDC handles rabies. Every dog entering or returning to the US needs a CDC Dog Import Form receipt. The form is free, filled out online, and the receipt is good for multiple entries over 6 months as long as your departure country does not change, so daily and weekly crossers fill it out once and reuse it. The dog must also appear healthy, be at least 6 months old, and have a microchip a universal scanner can read. Mexico is not on the CDC's high risk list for dog rabies, so you skip the extra rabies paperwork that applies to high risk countries, and there is no routine quarantine when you meet the requirements.
APHIS handles screwworm, and this is the requirement most people have not heard about. Mexico has been classified as screwworm-affected since November 2024, so a dog arriving from Mexico, including a US dog that just went down for the weekend, needs a screwworm freedom certificate. It has to be issued within 5 days before you cross and state that the dog was inspected and found free of screwworm. There is no APHIS template for it. On the Mexican side it does not have to come from a government office: an authorized MVRA clinical veterinarian can sign on behalf of the official government veterinarian, and SENASICA publishes a directory of the clinics and hospitals whose vets are authorized to do it. Find one near you before you need one, and assume you will need signed paper rather than a photo on your phone.
Cats are the easy case going south and a genuinely unclear one coming north. The CDC does not require a health certificate or rabies proof for a cat, though officers can inspect one and refuse a sick animal. The screwworm certificate is the open question. APHIS's own dog import page describes it as a dog requirement. The AVMA's guidance for the veterinarians who would actually sign the thing describes it as applying to dogs and cats arriving from Mexico. Those 2 readings have not been reconciled anywhere we could find, and the dogs-only version is the one a search hands you first, which is not a reason to trust it. If you cross with a cat, ask the port or an accredited vet before you go.
The things people forget
A few details trip people up more than the official rules do.
Keep a folder with the CDC form receipt, both screwworm certificates, proof of microchip, and recent vet records. You may cross 10 times without being asked for any of it, and then be asked on the 11th.
The microchip matters more than people think. If your chip is an older brand that a universal scanner cannot read, register or supplement it before you rely on it at the border. Age matters too, since the 6 month minimum for dogs is firm, so a young puppy may not qualify yet.
Timing your crossing helps as much as any document. Pets get hot and stressed in a long line, so avoid peak border waits, keep water in the car, and never leave an animal in a parked vehicle in the sun while you sort something out on foot.
The crossing itself is not the hard part anymore. The calendar is. 2 certificates, 2 vets, 2 countries, each one dead after 5 days. Plan the vet visits first and the trip follows.
Requirements last verified August 25, 2026, against APHIS's Pet Travel From the United States to Mexico page, last modified July 27, 2026, and APHIS's Bring a Pet Dog into the United States page, last modified April 1, 2026. The cat question is unsettled between those APHIS pages and the AVMA's guidance on traveling to and from Mexico with companion animals, so ask before you cross with a cat. Not read this pass, but where to go next: the NWS Inspection Certificate for Pet Dogs form your vet will fill in, and SENASICA's directory of authorized MVRA clinics and hospitals for finding the vet on the Tijuana side.