How Do I Get Rid of Mice in Walls?

University of Nebraska–Lincoln's Dennis Ferraro is direct on this point: indoor baiting should be avoided at all costs, because poisoned mice frequently retreat into the nearest void — often the wall itself — to die. An inaccessible carcass decomposes for weeks, producing a strong odor, attracting flies and maggots, and shedding bacteria into a space you can't clean. A trap you can find and empty avoids that outcome entirely.

Mice navigate largely by touch, running along walls guided by their whiskers rather than crossing open floor space. Follow droppings and grease marks to where mice actually emerge — gnaw holes near baseboards, gaps behind cabinet kick plates, and openings where pipes or utility lines penetrate the wall. Set snap traps flush against the wall right at those points, since that's where activity concentrates.

Keep trapping until you see no fresh droppings, gnawing, or noise for several days. Then pack the opening tightly with steel or copper wool — materials mice can't chew through — and caulk over it; use galvanized hardware cloth for larger gaps. Sealing before trapping confirms the wall is clear risks trapping a live mouse inside, recreating the exact decay problem poison would have caused.

Extensive wall-void activity, multiple exit points across several rooms, or noise that persists despite consistent trapping usually means access limitations a homeowner can't work around — behind finished walls, under built-ins, or inside multi-story chases. A pro with wall-access tools and thermal/acoustic inspection can locate activity you can't see from a baseboard gap alone.