If you're hearing scratching, scurrying, or squeaking inside your walls at night, mice in your walls are the most likely explanation — especially if you're also finding droppings, gnaw marks, or a musky odor nearby. Wall activity usually means mice have established a travel route or nest, not just wandered in once.
Key facts:
The timing and location of the noise matters:
If you're hearing activity during the day, that can indicate a larger infestation where competition for space is pushing mice out of their normal nocturnal pattern.
Mice aren't the only thing that makes noise in walls. Squirrels, rats, raccoons, birds, and settling pipes can all sound similar. A few things that point specifically to mice:
The more of these you have, the more confident you can be it's mice and not something else.
Trapping without sealing entry points is a losing game — new mice replace the ones you catch. Find the gaps first.
Common entry points:
Mice fit through a hole the size of a dime. Use a flashlight and inspect from the outside as well as inside. Mark anything you find before you seal, so you don't miss any.
Seal with steel wool packed into gaps and covered with caulk, hardware cloth, or sheet metal for larger openings. Mice chew through soft foam and regular caulk alone — material choice matters. Steel wool and expandable foam →
Place traps perpendicular to the wall with the trigger end facing the baseboard — that's where mice travel. Focus on areas near where you're hearing activity and anywhere you've found droppings.
Cut off their food supply at the same time:
Snap traps are the most effective option. The Victor Easy Set is the standard for good reason — sensitive, fast, easy to reset. Set more than you think you need: six to eight in an active kitchen is a starting point.
Don't use poison in a wall situation. A mouse that dies inside a wall after eating bait creates an odor problem that can last weeks and may be impossible to access. More on dead mouse smell →
If you found gnaw marks near wiring, or are hearing mice in walls adjacent to an electrical panel, outlet, or junction box — have a licensed electrician inspect the accessible wiring. Rodent damage to wire insulation creates arc faults, which are a recognized cause of residential fires.2 This is worth taking seriously in any established wall infestation.
It happens even with trapping. The smell is unmistakable — a sweet, sickly odor that gets stronger before it fades. It typically peaks around day 3–5 and can last 1–3 weeks depending on the size of the mouse and the temperature.
There's usually no practical way to remove it without opening the wall. The fastest path through it is airflow — fans, open windows, and an odor absorber like activated charcoal placed near the smell source. It will resolve on its own.
Assume there are droppings anywhere mice have been active. Don't dry sweep or vacuum them — that puts contaminated dust in the air. The CDC recommends spraying with disinfectant first, letting it sit five minutes, then wiping with paper towels and disposing in a sealed bag.3 Wear gloves throughout.
A pest professional can do a full structural inspection, identify entry points you missed, and set up a monitoring plan so you know when the problem is actually resolved.
Connect with a local pest control expert →