How to Keep Mice Out of Your Garage This Winter (Step-by-Step Guide)

When the first cold snap hits, mice will start looking for three things: heat, shelter, and calories. Garages check all three boxes — insulated spaces, stacked boxes and fabric for nesting, and snacks like bird seed, pet food, or the odd granola bar left in a cup holder. 

All they need is the tiniest opening (as small as a pencil), to move in fast. And an infestation is more than a health hazard — it can be costly, too.

Rodents put your vehicle at serious risk, and repairing the damage they cause is often complicated and expensive. That’s why we’ve put together this guide: to help you recognize the warning signs, create a mouse-proofing plan for your garage, and protect your valuables before winter sets in.

Quick Signs You Might Have a Mouse Problem

You’ll often know you have a mouse problem long before you see a mouse. For being so tiny and “quiet,” they’re rarely subtle guests. Keep an eye out for:

• Droppings (small, dark, rice-shaped pellets) along walls, behind bins, or under shelves
• Gnaw marks on cardboard, wood, wiring insulation, or bags of seed
• Shredded nesting material: paper, insulation, fabric, or seat stuffing
• Strange odors that may smell musty or ammonia-like.

If you spot these, or any of the other telltale signs of a mouse infestation, it’s time to take action. 

How to Mouse-Proof Your Garage for the Winter

Think of this as a one-two punch: remove what attracts, then block how they enter. Do these in order and you’ll see a noticeable difference.

1) Get the mice out

Before you do anything, make sure the mice currently inside are gone — otherwise, you risk trapping them in when you seal up your garage.

Start by setting several traps along walls, behind storage bins, and near any signs of activity. If you’re unsure, you can check out our full guide on Where to Put Mouse Traps for Best Results. Snap traps are generally the most reliable, though live traps work if you prefer a no-kill approach.

• Placement: Put snap or live traps perpendicular to walls (trigger against the wall), where mice naturally travel.
• Bait: A tiny smear of peanut butter works; don’t overdo it.
• Coverage: A few traps won’t cut it — think several along the common paths, 6–10 feet apart.
• Check daily: Reset for a week. If nothing happens, you’ve likely made progress.

2) Remove all attractants

The more boring your garage is to a mouse, the less likely they are to stick around. It sounds simple, but it works. Before it gets too cold, do a little fall cleaning:

• Secure food: Store pet food, bird seed, and pantry overflow in hard, sealed containers. No plastic bags or paper boxes.
• Manage trash & recycling: Empty regularly, rinse containers, use cans with lids. If it’s possible to store elsewhere, even better.
• Eliminate cardboard & fabric: Mice love nothing more than turning cardboard and fabric (blankets, camping gear, decorations) into a cozy nest. Latch them away in bins or remove entirely.
• Vehicle snacks: Clear out glove boxes, door pockets, and consoles. A single snack wrapper can invite nightly scouting.

3) Seal every opening (no matter how small)

If you can see through it, a mice can squeeze through it. Grab a flashlight, get down to floor level, and begin your “gap hunt.” Try turning the lights off to spot any cracks of daylight sneaking through.

Take your time on this step. Sealing is the most important thing you’ll do.

What to use: Pack in copper mesh or steel wool, then seal with exterior caulk or foam. Large openings can be covered with ¼-inch hardware cloth (metal screen).

Where to look:

• Around utility lines and pipes.
• Along the bottom edge where the wall meets the slabs.
• At side- and top-of-door seals
• Around windows.
• At the garage-to-house door threshold and its weatherstrip.
• Any old cable holes.

Vents & drains: Add screens where appropriate so air moves but mice can’t.

4) Secure the garage door

Years of foundation settling can cause a garage door to no longer sit flush along the floor. If you suspect their might be gaps to be exploited, you can find garage door seals at most home improvement stores.

• Bottom seal: Replace cracked or flattened rubber. Consider a threshold strip on the floor for a tighter seal if the slab is uneven.
• Sides and top: Check the vinyl weatherstripping and replace if brittle or loose.
• Edge protection: If mice have chewed the door jambs before, add rodent-shield plates along the lower side jambs to remove their bite point.

A well-sealed door stops most drive-by entries before they start.

5) Install a Box-Kat around your vehicle

For many, their vehicle is the second-largest expense outside of their home. Why risk expensive rodent damage that can leave your car in the shop for weeks?

Instead, install a Box-Kat mouse barrier around the vehicle to ensure that no mice are able to find their way near your car. It creates a durable, flexible perimeter that prevent entry and protects wiring, filters, and upholstery from ever becoming a target.

Unlike sprays or oils, the Box-Kat doesn’t just deter mice — it stops them in their tracks.

Do Rodent Repellents Actually Work?

Search the internet for rodent deterrents and you’ll find a lot of advice that centers around essential oils, fragrant sprays, ultrasonic devices, soap bars, and a whole bunch of other repellents that are “sure to keep the mice away.”

But do they work?

The short answer: Maybe, briefly, sometimes — but certainly not reliably.

If there’s food or shelter on the line, no repellent alone will keep the mice away. They are extremely adaptable pests who will go to great lengths to survive. Annoying scents or sounds will only do so much.

Feel free to use them in conjunction with the measures listed above, but remember that physical prevention is the only surefire way to keep mice away.

A Quick Word on Poisons — Why Not to Use Them

Rodenticides can harm pets and wildlife and may be restricted in your area. They also leave you with an animal that dies in hard-to-reach places. For a garage, the most responsible and effective approach is the one you’ve just read: remove attractants, seal openings, harden the door, and trap as needed.

If an infestation is severe or persistent, consider a licensed professional who prioritizes exclusion over poisons.

A Simple Rodent-Proofing Routine (5 Minutes, Once a Month)

Set a reminder on your phone for the first weekend of each month, November through March, to give your garage a quick inspection:

• Walk the edges: Look for fresh gnawing, droppings, or new gaps.
• Check seals: Make sure the bottom seal still contacts the floor all the way across.
• Audit storage: Lids tight, no new cardboard piles, no seed bags on the floor.
• Vehicle check: Glove compartment and trunk free of snacks; quick peek under the hood for nesting.

A tiny habit like this will keep any potential problems small!