Southwest is one of the most popular airlines for pet owners, and for good reason: no change fees, straightforward pricing, and a relatively simple pet policy. But there are still rules you need to know before booking.

Here’s everything you need to know about flying with your dog on Southwest.

The Quick Answer

Southwest Pet Policy Details

What’s Allowed

Southwest allows small dogs and cats in the cabin. That’s it — no other animals (except trained service animals).

• One pet per passenger — You can’t bring two dogs even if they’d fit in one carrier
• Pet must stay in carrier — For the entire flight, under the seat in front of you
• Carrier counts as carry-on — You still get one personal item

Weight Limits

Southwest doesn’t have an official weight limit, but your pet + carrier must fit completely under the seat in front of you. Realistically, this means:

• Dogs under ~15-17 lbs
• Carrier dimensions max: 18.5" L x 8.5" H x 13.5" W

If your dog is pushing 20 lbs, it’s going to be tight. And if they don’t fit, you won’t be allowed to board.

No Cargo Option

Southwest does not transport pets in cargo. If your dog is too large for the cabin, Southwest is not an option. Period.

For larger dogs, you’d need to look at Delta, United, or American — all of which have cargo programs (with significant restrictions).

Fees

• $125 each way — Paid at the airport, not online
• Cash, credit, or debit accepted
• Each direction is charged separately — Round trip = $250 total

The fee is per carrier, not per pet. But since Southwest only allows one pet per passenger, this is effectively per pet.

How to Book

1. Book your flight first — You cannot add a pet during online booking
2. Call Southwest — 1-800-435-9792 — to add your pet to the reservation
3. Or add at the airport — Arrive early and tell the agent at check-in
4. Pay at the gate — Pet fee is collected when you check in

Important: Southwest limits the number of pets per flight (usually 6). Call ahead to make sure there’s space, especially on popular routes.

Carrier Requirements

Your carrier must:

• Be soft-sided or hard-sided (soft-sided is easier to fit)
• Fit completely under the seat (18.5" x 8.5" x 13.5" max)
• Be leak-proof and well-ventilated
• Allow your pet to stand and turn around
• Stay closed for the entire flight

Recommended Carriers

Look for carriers specifically designed for airline travel. Popular options:

• Sherpa Original Deluxe — Airline-approved, fits most under-seat spaces
• Sleepypod Air — Crash-tested, premium option
• AmazonBasics Soft-Sided Carrier — Budget-friendly, gets the job done

Always measure your carrier against Southwest’s dimensions before flying.

Breed Restrictions

Southwest has no breed restrictions for in-cabin pets. Pit bulls, Rottweilers, and other commonly restricted breeds are allowed in the cabin (as long as they fit in a carrier under the seat — which, realistically, they won’t).

This is different from cargo policies at other airlines, which often restrict snub-nosed breeds.

Tips for Flying Southwest with Your Dog

1. Book Early Boarding

Southwest’s open seating means early boarding = better seat selection. With a pet, you want:

• A window seat (more floor space for carrier)
• Avoid bulkhead rows (no under-seat storage)
• Avoid exit rows (pets not allowed)

Pay for Early Bird Check-In or check in exactly 24 hours before departure.

2. Choose Direct Flights

Every connection is another opportunity for stress. Book direct whenever possible.

3. Exercise Before the Flight

Tire your dog out before heading to the airport. A sleepy dog is a quiet dog.

4. Skip Food Before Flying

Feed your dog 4-6 hours before the flight to avoid upset stomachs. Water is fine.

5. Bring Essentials in Your Personal Item

• Poop bags
• Paper towels
• Treats
• Collapsible water bowl
• Puppy pad (in case of accidents in carrier)

6. Potty Before Security

Most airports have pet relief areas before and after security. Use them.

What to Expect at the Airport

Check-In

• Tell the agent you’re traveling with a pet
• Pay the $125 fee
• They may ask to see your pet and carrier

TSA Security

• You carry the dog — Remove your dog from the carrier
• Carrier goes through X-ray — Like any other bag
• Walk through with your dog — Carry them or walk them on leash through the metal detector
• Put dog back in carrier immediately after screening

This is the most stressful part for most dogs. Practice at home if possible.

Boarding

• Board with your group
• Store carrier under the seat in front of you
• Carrier must stay closed and under the seat for the entire flight

During the Flight

• Your dog must stay in the carrier
• You can reach in to comfort them
• Keep the carrier zipped/closed

Frequently Asked Questions

Can I buy a seat for my dog?

No. Southwest does not allow pets in seats. The carrier must go under the seat in front of you.

Can I bring two dogs?

Only if you’re traveling with another person. Each passenger can bring one pet in one carrier.

What if my dog barks the whole flight?

This is why preparation matters. A tired, comfortable dog is less likely to bark. If your dog has severe anxiety, talk to your vet about options before flying.

Can I fly with a puppy?

Yes, but puppies must be at least 8 weeks old.

Are emotional support animals free?

No. As of 2021, Southwest (like most airlines) no longer recognizes emotional support animals. Only trained psychiatric service dogs fly free.

What about service dogs?

Trained service dogs fly free and are not required to be in a carrier. Southwest requires documentation submitted in advance.

The Bottom Line

Southwest is a solid choice for flying with small dogs:

• Pros: No change fees, simple policy, no breed restrictions, points are easy to earn
• Cons: No cargo option, limited pets per flight, fee adds up on round trips

If your dog fits comfortably in an under-seat carrier, Southwest works well. If your dog is over ~15 lbs, it’s going to be a squeeze — and over ~20 lbs, you’ll need to look at other options or drive.

Read next: Delta Pet Policy | United Pet Policy | American Airlines Pet Policy