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The best time to keep mice out of your garage is before the first cold snap sends them looking for shelter. A garage gives mice almost everything they want: it’s out of the wind, full of boxes to nest in, and often stocked with birdseed, grass seed, and pet food. And for a lot of homes, it’s the easiest way into the house.
This guide covers why mice end up in your garage, the signs they’ve already moved in, the 8 steps to keep mice out of your garage for good, how to protect your car, and how to clean up safely if they’ve already been there.
WHAT’S IN THIS GUIDE
Why Mice Move Into Your Garage
House mice are looking for three things every fall: shelter, food, and a warm place to nest. A typical garage has all three. Mice live in piles of debris, stored items that rarely get moved, stacked wood, and insulation, according to University of Nebraska Extension. Add a bag of birdseed or dog food on the floor and a garage door that doesn’t seal at the bottom, and you’ve built them a winter home. Source: University of Nebraska–Lincoln Extension — Controlling House Mice
A couple of mice can become a big problem fast. Nebraska Extension notes that in ideal conditions, a female can raise 5 to 10 litters a year, with 5 to 6 young in each, and the young can breed in as little as 6 weeks. That’s why it pays to keep mice out of your garage before they settle in, not after.
Mice don’t need much room to get in, either. UC IPM says house mice can squeeze under gaps just 1/4 inch tall and through openings 3/8 inch wide. A worn garage door seal is plenty. Source: UC IPM — Pest Notes: House Mouse
Signs of Mice in Your Garage
Mice in your garage usually leave clues before you ever see one. Grab a flashlight and check the corners, behind shelves, and under anything stored on the floor for:
- Droppings. Small, dark, and scattered, usually along walls and in corners.
- Chewed bags. Holes in bags of birdseed, grass seed, or pet food, with spilled seed or kibble on the floor.
- Holes in cardboard. Nebraska Extension says mice typically gnaw clean-cut holes about 1 1/2 inches across in cardboard boxes.
- Nests. Balls of shredded paper, fabric, or insulation tucked into boxes, drawers, or the back of a shelf.
- Signs in your car. Seeds or nesting material under the hood or in the air filter housing.
If you’re hearing scratching inside the house too, they may already be past the garage. Here are the signs of mice in walls and how to confirm them.
How to Keep Mice Out of Your Garage in 8 Steps
These steps work best in this order: seal the ways in, take away the food and shelter, then trap any mice that are already inside.
Step 1: Check the garage door seal
If you want to keep mice out of your garage, start with the bottom of the door. It’s the most common way in. On a sunny day, close the door, turn off the lights, and look along the bottom from inside. If you see daylight anywhere along the seal, a mouse can get through it. Remember, UC IPM says a gap 1/4 inch tall is enough.
If the rubber is cracked, flattened, or torn, replace it. A new garage door bottom seal slides into the track on the bottom of most garage doors and takes about 30 minutes to put in. Check the weatherstripping along the sides and top of the door while you’re at it.
Step 2: Close the gap from an uneven floor
Sometimes the seal is fine but the concrete isn’t. If your garage floor has settled or dips in one spot, the door can’t seal all the way across no matter how new the rubber is. A garage door threshold seal glues to the floor right under the door and fills that low spot, so the door closes down onto it. It’s a cheap fix that goes a long way to keep mice out of your garage.
Step 3: Seal gaps around pipes, wires, and walls
Walk the inside of the garage and look low on every wall, especially where pipes, wires, cables, and the dryer vent come through, and where the walls meet the slab. Nebraska Extension says to close every opening 1/4 inch or larger. For bigger gaps, it recommends copper mesh or a stainless steel fiber filler. Source: University of Nebraska–Lincoln Extension — Controlling House Mice
Pack the gap tight with copper mesh and seal over it with sealant or mortar. Don’t rely on expanding foam alone. UC IPM says foam, rubber, plastic, and wood are all ineffective for plugging mouse holes, because mice chew right through them. Source: UC IPM — Pest Notes: House Mouse
Step 4: Cover vents and larger openings
Garage vents and other openings that need to stay open for airflow should be covered with 1/4-inch hardware cloth screwed or stapled in place. Nebraska Extension lists 1/4-inch wire mesh, aluminum flashing, and concrete as good choices for larger openings.
Step 5: Seal the door into your house
This is the step most people miss. Even if a mouse gets into the garage, the door into your house should stop it. Nebraska Extension says doors should fit tightly. If you can see light under the door from the garage side, add a door sweep and check the weatherstripping around the frame. Our guide on how to keep mice out of your house covers sealing the rest of the outside.
Step 6: Store seed and pet food in metal cans
Birdseed, grass seed, and pet food are the biggest reasons mice in your garage stick around once they find it. Nebraska Extension recommends securing food, including pet food, and modifying bird feeders to cut off their food supply. Paper bags and thin plastic tubs won’t do it. UC IPM warns that mice can chew through storage containers meant to protect food. Source: UC IPM — Pest Notes: House Mouse
A galvanized metal trash can with a tight lid works best. Pour the bag right in, and sweep up any spilled seed or kibble.
Step 7: Get stored items off the floor and away from the walls
Clutter is shelter for mice in your garage. Nebraska Extension recommends keeping stored materials at least 8 inches off the ground and at least 1 foot away from walls, so mice have fewer places to hide and you can spot droppings. Source: University of Nebraska–Lincoln Extension — Controlling House Mice
Move things up onto a heavy-duty garage shelving unit and swap cardboard boxes for heavy-duty stackable bins with lids. Our guide on how to organize a garage walks through setting up shelves, bins, and zones.
Step 8: Keep the door closed and set traps along the walls
Utah State University Extension says to keep all exterior doors closed. That includes not leaving the big door open for hours on fall evenings. Then set a few traps to catch any mice that are already inside. Source: Utah State University Extension — House Mouse
UC IPM says house mice rarely go more than 30 feet from their nest, so put traps where you found droppings. Place snap traps close to the walls with the trigger facing the wall, so mice run right over it, and space them no more than about 10 feet apart. A small dab of peanut butter is an easy bait. If you’d rather not kill them, a catch-and-release mouse trap works too. Check it at least twice a day. Source: UC IPM — Pest Notes: House Mouse
Keep a couple of traps set along the walls all winter. A trap that catches nothing tells you you’ve managed to keep mice out of your garage.
Protect Your Car From Mice
Your car is a big part of why it matters to keep mice out of your garage. Griffin Dill, a pest management specialist with University of Maine Cooperative Extension, says mice like to nest in vehicles in the winter, and cars offer ideal shelter. Rodents can chew wires and hoses and pack the air filter with nesting material and stored food. He recommends parking in a mouse-proof garage when you can, because a car parked in or near tall grass is inviting to them. Source: University of Maine — Keeping Rodents Out of Your Vehicle
A few habits help:
- Pop the hood every few weeks in fall and winter and look for nesting material, seeds, or droppings, especially on top of the engine and around the air filter.
- Check the cabin air filter if the heater starts to smell musty.
- Don’t keep pet food, birdseed, or grass seed in the car or on the floor near it.
- If you find chewed wires, have a mechanic look before you drive it.
How to Clean Up After Mice in the Garage
If there have been mice in your garage, clean up carefully. Mouse droppings and urine can spread diseases, including hantavirus, so don’t sweep or vacuum them. That puts dust from the droppings into the air you breathe. The CDC recommends:
- Open the doors and windows for 30 minutes before you start, and leave the area while it airs out. For a garage, that means opening the big door.
- Wear rubber or plastic gloves. Put work gloves over them if you’re moving traps and debris.
- Spray droppings, urine, and nests with a disinfectant or a fresh mix of 1 1/2 cups of bleach in 1 gallon of water, and let it soak for 5 minutes.
- Wipe it up with paper towels and throw them away in a sealed bag.
- If mice were in your car, open the hood, doors, and trunk and let it air out for 20 minutes before you clean.
Source: CDC — How to Clean Up After Rodents
When to Call a Pro
Most of the time you can keep mice out of your garage yourself, but call a pest control professional if:
- You’re still catching mice after two or three weeks of trapping
- You can’t find where they’re getting in
- The droppings are 1/2 inch or longer, which points to rats
- Mice have chewed wiring in your car or the walls
- You’re finding signs of mice in the house, not just the garage
Sealing the garage is part of the bigger fall job of getting your home ready for cold weather. See our winter home maintenance checklist for the rest.
Frequently Asked Questions About Mice in the Garage
Why do I have mice in my garage?
Most mice in your garage moved in during the fall, looking for shelter and food. Gaps under the garage door, clutter to nest in, and open bags of birdseed, grass seed, or pet food make a garage an easy place to spend the winter.
How do mice get into a garage?
Most often under the garage door, through a worn bottom seal or a gap where the floor has settled. They also come in through gaps around pipes and wires, vents without screens, and an open door. UC IPM says they can fit under a gap just 1/4 inch tall, so sealing the door is the first step to keep mice out of your garage.
Will mice in the garage get into the house?
They can. Garages often connect to the house through the entry door, gaps around pipes and wires, and attic spaces. A door sweep and good weatherstripping on the door into the house are your best defense.
Does leaving a light on in the garage keep mice away?
Not reliably. Mice prefer the dark, but they get used to light, especially once they’ve found food and shelter. Sealing the gaps and removing food works much better than lights or sound.
What is the best bait for mice in a garage?
A small dab of peanut butter is easy and works well. UC IPM notes that the best bait is often the food the mice are already eating, so if they’ve been into the birdseed, a few seeds stuck in a little peanut butter works great.
What do I do if mice have been in my car?
Open the hood, doors, and trunk and let the car air out for 20 minutes, then clean up any droppings and nests with gloves and disinfectant. Check the air filter and look for chewed wires and hoses, and have a mechanic check anything that’s been chewed.