How to Get Rid of Mice in a NYC Apartment

The single most important thing to know

Every NYC mouse problem has the same root cause: an unsealed gap. New York has persistent rodent pressure — dense housing where buildings share basements and risers, restaurant waste, and an underground sewer system that functions as a rodent highway. You can trap your way to an empty apartment in a week, leave the gap under your sink pipe open, and have new mice within a fortnight. This guide works through exclusion first, then trapping, because that’s the order that actually solves it.

Confirming it’s mice (not rats)

Before treating, confirm what you’re dealing with. Mice leave small, dark, rice-grain-sized droppings (6–8mm), primarily along walls, inside cabinets and under appliances. They make light scratching sounds in walls and ceilings at night. Runways — the paths mice use repeatedly — leave faint smudge marks from body grease along skirting boards and pipes.

Rats leave much larger droppings (12–20mm), make heavier thumping noises, and create obvious burrows. Treatment differs significantly, so confirm before acting. See rats vs mice — how to tell the difference in NYC.

Step 1: Map every entry point

A mouse squeezes through a gap 18mm across — the diameter of a dime. Do a systematic sweep before sealing anything:

• Under every sink: the gap where supply and drain pipes exit through the cabinet wall or floor
• Behind appliances: behind the stove (especially around the gas line and anti-tip bracket area), behind the fridge, behind the dishwasher
• Cabinet kick-boards: the strip at floor level under kitchen and bathroom cabinets; mice commonly chew through these or enter at the joints
• Radiator and heating pipes: where pipes enter and exit through walls and floors; these gaps are often left large in older NYC buildings
• Utility penetrations: electrical conduits, cable TV lines, HVAC ducts
• Under doors: a gap larger than a business card (about 10mm) is an entry point

Mark every gap. Missing one means the exclusion fails.

Step 2: Seal with materials mice can’t chew

Most DIY sealing fails because it uses foam or soft caulk alone — mice gnaw through both. The correct sequence:

1. Pack the gap with steel wool — mice can’t chew through it, and it stuffs easily into irregular gaps around pipes
2. Secure with hardware mesh (1/4-inch hardware cloth) stapled or screwed over larger openings
3. Apply rodent-resistant sealant over the top — expandable foam rated for pests, or quality silicone caulk
4. Under doors: fit a metal door sweep that sits flush to the floor. A solid metal sweep is more reliable than brush-type seals, which often leave a gap.

For pipe penetrations, rodent-proof escutcheon plates (pipe covers that sit flush against the wall and leave no gap) are a cleaner and more permanent fix.

Step 3: Snap traps on the runways

Mice avoid open spaces. They run along walls, behind objects and inside cabinets. Set traps on these routes:

Placement: flush against the wall, perpendicular to it, with the bait trigger touching the wall surface. Inside cabinets under sinks, behind the stove, along the skirting board in active rooms.

Bait: a pea-sized amount of peanut butter on the trigger. Too much and mice steal it without triggering the trap. Chocolate hazelnut spread and cotton wool (for nesting) work well too.

Quantity: more than you’d expect. Six to ten traps across an active apartment is not excessive. Mice are cautious around new objects (neophobia), so the more traps placed, the higher the encounter rate.

Maintenance: check and reset every 24 hours. A dead mouse left in a trap stops working, attracts flies and signals danger to other mice.

Step 4: Remove food and harbourage

Mice stay where there’s food and shelter. While exclusion is the core fix, removing attractants accelerates results:

• Hard-sided sealed containers for all dry goods, including pet food — mice chew through plastic bags and thin-walled bins
• Fix any leaking pipes or taps
• Remove cardboard boxes, stacked paper and fabric piles that provide nesting material
• Clean behind and under appliances where crumbs accumulate

Step 5: Involve the building

This is the step most tenants skip, and the main reason mouse problems recur.

In NYC’s multi-unit buildings, mice move through shared wall voids, pipe chases, risers and basements. A sealed and trapped apartment is only as effective as the building around it. If the basement has an active population, or an adjacent unit has an open gap, new mice enter your apartment repeatedly.

What to do:

• Report the infestation to management in writing — email or letter, which creates a record
• Request a professional exterminator for the building, not just your unit
• If management doesn’t respond, file a complaint via NYC 311 (Housing Maintenance Code § 27-2018)

Under the NYC Housing Maintenance Code, owners must keep dwelling units free of pests. Mice are the landlord’s responsibility in rental housing. See landlord vs tenant pest responsibilities in NYC.

When to call a professional

Call a licensed exterminator if:

• Trapping for two to three weeks with correct setup and activity continues
• You can’t find or access the entry points (common in older buildings where gaps are inside wall voids or above ceilings)
• The problem spans multiple rooms or appears to be coming from inside walls rather than accessible gaps
• Building management has arranged building-wide treatment and you need your unit treated as part of that

A professional exclusion inspection uses UV light, and familiarity with the common entry points in different NYC building types — pre-war walkups, post-war slabs and brownstones each have different structural weak points. They can also coordinate with building management on building-wide treatment, which is often necessary for lasting results.

See our rodent control service for NYC apartments and buildings.