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Will Mothballs Keep Squirrels Away — No, and 3 Fixes

Will mothballs keep squirrels away, and is it even legal? No on both counts, and 3 measures close the gap instead. See which fits your roof.

By Zakaria 4 min read Save to Pinterest — opens Pinterest in a new tab

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A grey squirrel foraging on a bright green lawn
Photo: PollyDot, Pixabay Content License, via Pixabay
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It does not work, and in the United States it is against federal law — scattering mothballs anywhere other than a sealed box of clothes is using a pesticide against its label.

Why they fail

A squirrel with a nest, a litter or a food cache in your roof has invested heavily in that site. A strong smell is an inconvenience, not an eviction.

What actually happens:

  1. Day one or two: the squirrel avoids the immediate area. This is the bit people report
  2. Week one: it works around them, using a different route through the same space
  3. Week two onward: completely ignored
  4. Meanwhile: the mothballs are still there, still sublimating, still in your house

Extension services and wildlife agencies are consistent on this, and the manufacturers make no such claim — no mothball product is registered against any mammal.

Mothballs are a registered pesticide. Under US federal law it is illegal to use a pesticide in a manner inconsistent with its labelling, and the label is specific: sealed containers, with fabrics, to kill clothes moths.

An attic is not a sealed container. Neither is a garden bed or a burrow.

The realistic penalty is your own house

Enforcement action happens, but the common outcome is worse in practice: a crawl space or attic that smells of naphthalene for years, a vapour that will not clear, and in some cases remediation work.

It is far easier to scatter them than to get rid of them.

What is actually in them

The two chemicals
NaphthaleneParadichlorobenzene
FormSublimates to vapourSublimates to vapour
Acute riskHaemolytic anaemiaLiver and kidney effects
ClassificationPossible human carcinogenPossible human carcinogen
ChildrenIngestion is a medical emergencySame
In soilPersistent, leachesPersistent, leaches

The vapour is the point of the product, and it does not stay where you put it. In an attic it moves into the rooms below through ceiling penetrations, light fittings and ductwork.

If a child or pet swallows one, call poison control immediately. They look like sweets, and a single mothball is a serious dose for a small body.

Outdoors is worse

Scattered in a garden, around a shed or down a burrow, mothballs:

  • Leach toward groundwater and do not break down quickly
  • Kill soil organisms in the treated area
  • Get eaten by birds, pets and wildlife
  • Reach non-target animals if pushed into burrows — snakes, toads, nesting bees

Cleanup: pick up every visible mothball with gloves and bag it for hazardous waste disposal. Where a lot were used, the soil itself has to come out.

Why the advice will not die

Because the first two days are real. A squirrel does back off from a freshly opened box, someone notices, and the story gets told before the squirrel comes back.

The same false positive explains the rest of the list:

  • Predator urine — they live alongside actual predators
  • Peppermint oil, cayenne, garlic — a few days at most, and rain ends it
  • Human hair, soap shavings — nothing
  • Ultrasonic repellers — tested repeatedly, no effect
  • Vibrating stakes — habituated within a week

Nobody writes the follow-up post three weeks later.

What to do instead

If it works by smell, it does not work

That single test filters almost every product marketed for this problem. A squirrel problem is solved by making the space physically inaccessible, and by nothing else.

In a roof or attic:

  • Cut branches back at least ten feet from the building. This is usually the whole entry route
  • Cap chimneys and vents with metal mesh
  • Repair rotten fascia, soffit and trim — soft wood is an invitation
  • Cover gaps with half-inch hardware cloth. Not foam, not plastic, not steel wool: they chew through all three
  • Use a one-way exclusion door to let residents out without letting them back
  • Do the work in autumn, between the two breeding seasons — sealing a hole in February can trap a litter inside the roof

In the garden:

  • Hardware cloth cages over bulbs, seedlings and vulnerable beds
  • Genuinely squirrel-proof feeders, on a baffled pole away from any launch point
  • Clean up spilled seed and fallen fruit, which is what drew them in
  • Bulb cages at planting time, which costs nothing compared with replanting

The hardware cloth is unglamorous and it is the only thing on this page that holds.

Our picks

#PickBest forWhere to buy
1Hardware cloth, 1/2 inWhat actually closes a gap Check price for Hardware cloth, 1/2 in →
2One-way exclusion doorGets residents out without letting them back Check price for One-way exclusion door →
3Chimney and vent capsCloses the routes people forget Check price for Chimney and vent caps →

What actually closes a gap

Hardware cloth, 1/2 in

A squirrel problem is solved by making the space physically inaccessible, and by nothing else. This is that, in a roll.

Mesh
1/2 in galvanised
Not
Foam, plastic or steel wool — they chew through all three
Covers
Soffit and fascia gaps, vents, weep holes
Fix
Screws and washers, not staples

What we liked

  • The only common material a squirrel cannot chew through
  • Permanent once fitted properly
  • Also excludes rats, mice and birds
  • Cheap relative to the roof damage it prevents

Worth knowing

  • Cutting it is unpleasant; wear gloves
  • Every gap must be found, or the work is wasted
Check current price (affiliate link, opens in a new tab)

Gets residents out without letting them back

One-way exclusion door

Fit this, confirm the attic is empty, then close the hole with hardware cloth. Never seal a hole without knowing what is behind it.

Fits
Over the active entry hole
Lets
Animals out, not back in
Check
No dependent young before fitting
Then
Seal the hole permanently

What we liked

  • Avoids sealing an animal inside, which is both cruel and a smell problem
  • No trapping, no handling, no relocation
  • Cheap relative to a pest-control visit

Worth knowing

  • Must not be used in spring when young may be in the nest
  • Only works if every other entry is already sealed
Check current price (affiliate link, opens in a new tab)

Closes the routes people forget

Chimney and vent caps

The entry nobody inspects until something is living behind it. Cap them while you are sealing everything else.

Covers
Chimney flues, roof vents, dryer and bathroom outlets
Material
Stainless or galvanised mesh
Also stops
Birds nesting in the same openings
Fit
Clamp or screw to the flue

What we liked

  • Chimneys and vents are a common entry and rarely checked
  • Stops birds and raccoons as well
  • Lasts years with no maintenance

Worth knowing

  • Roof work, so a job for someone comfortable up there
  • Must not restrict a flue's draught
Check current price (affiliate link, opens in a new tab)

Common questions

Do mothballs keep squirrels away?

No. Mothballs are sometimes avoided by a squirrel for the first day or two, then completely ignored — an animal with an established nest or food cache will tolerate the smell rather than give up the site. Every pest control extension service that has looked at it reaches the same conclusion, and the manufacturers do not claim it either: no mothball product sold in the United States is registered for use against squirrels, rodents or any mammal apart from the moths on the label.

Is it illegal to use mothballs against squirrels?

In the United States, yes. Mothballs are a registered pesticide, and federal law makes it illegal to use any pesticide in a way inconsistent with its labelling. The label specifies use in a sealed container with fabrics, which is exactly the use scattering them in an attic, a garden bed or a burrow is not. It is enforceable, and people have been fined — but the more common consequence is a contaminated crawl space and a house that smells for years.

Are mothballs dangerous to have in an attic?

They can be. Mothballs are naphthalene or paradichlorobenzene, both of which sublimate into a vapour you are then breathing, and in an unsealed attic that vapour moves into the living space below through ceiling gaps and ductwork. Naphthalene exposure can cause haemolytic anaemia, and children and pets are at real risk if they find and swallow one, since they resemble sweets. Both compounds are classified as possible human carcinogens.

What happens if mothballs are scattered outdoors?

They contaminate the soil and whatever drains through it, and they do not break down quickly. The chemical leaches toward groundwater, kills soil organisms, and can be picked up and eaten by birds, pets and wildlife. Once they are in a garden bed the only remedy is removing the visible mothballs with gloves and, if a lot were used, excavating the soil — so the decision to scatter them is harder to undo than to make.

What actually keeps squirrels out?

Physical exclusion, every time. For a roof that means cutting branches back at least ten feet from the building, capping vents and chimneys with metal mesh, repairing rotten fascia and soffit, and covering gaps with half-inch hardware cloth rather than anything a squirrel can chew. In the garden it means hardware cloth cages over bulbs and seedlings and genuinely squirrel-proof feeders. Nothing that works by smell resolves a squirrel problem, which is the one lesson worth taking from the mothball question.

Why does this advice keep getting repeated?

Because a squirrel really does avoid a freshly opened box for a day or two, and that short window is enough for someone to believe it worked and pass it on. The same pattern explains the persistence of predator urine, peppermint oil, cayenne, human hair and ultrasonic devices — a brief novelty response gets mistaken for a solution, and nobody writes the follow-up post three weeks later when the squirrel came back.

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