Do Marshmallows Go Bad or Expire? Shelf Life, Storage and Signs

That half-open bag of marshmallows has been in the back of the pantry since the last campfire, and now there’s a sweet potato casserole to make. Toss them or use them? Here’s how long marshmallows last, why they turn hard, and what really means they’ve gone bad.

Do marshmallows go bad?

For a complete pantry storage reference, see our Food Storage Guide. Marshmallows are a pantry staple of hot cocoa season, so see our guide on whether hot cocoa mix goes bad too.

How Long Do Marshmallows Last?

It depends on which extension chart you read. These are cupboard storage estimates for quality, not guarantees, and we mark below which figures are labeled unopened.

Recent editions disagree. NDSU (2023), New Mexico State (2025) and K-State (2026) say 1 year. The Idaho, Oregon State and Washington State chart (2023) says 2 to 4 months, and the Texas A&M chart (2022) says 2 to 3. We found no chart that explains the difference. NDSU’s own figure moved from 2 to 3 months in 2013 to 1 year in its current guide.

How Long Do Unopened Marshmallows Last?

Published estimates run from about 2 months to a year. NDSU Extension’s Food Storage Guide, reviewed in January 2023, lists unopened marshmallows at 1 year. K-State Research and Extension’s cupboard storage guide, revised in June 2026, lists marshmallows at 1 year at 70°F, and New Mexico State University’s E-118, revised in April 2025, gives 1 year unopened. A 2023 publication from the University of Idaho, Oregon State and Washington State gives 2 to 4 months at 70°F, and Texas A&M AgriLife Extension gives 2 to 3 months. The University of Georgia chart (2011) gives 2 to 4 months, and Ohio State (2010) gives 2 to 3.

NDSU’s April 2013 edition, which is hosted on Purdue Extension’s site, gave 2 to 3 months. The shorter figure you may see elsewhere therefore has extension backing. Several of these charts don’t say whether the figure is for opened or unopened marshmallows, so we’d treat the shorter ones as general pantry estimates.

We’d follow the Best By date and storage instructions on your bag. The Idaho, Oregon State and Washington State publication says its times are approximate cupboard times for best quality, and that they depend on storage temperature and humidity, packaging and the food itself. K-State advises a cool, dry, dark spot away from heat sources such as appliances and sunlight.

USDA’s food product dating page says product dates are about quality rather than safety, except on infant formula. A bag past its Best By date isn’t automatically unsafe, but quality may have slipped. Check the signs below first.

How Long Do Opened Marshmallows Last?

NDSU gives opened marshmallows 1 month and says to keep them in an airtight container. It is the only chart we read with an opened-marshmallow figure. The others give one marshmallow row and, where they add a note, say airtight container. Some food sites say a week or two once opened, and we found no extension source for that. We’d press the air out of the bag, seal it in a jar or a zip-top bag with a tight closure, and use it first.

That 1 month is a quality estimate. A bag that’s a bit older but still soft and free of the signs below isn’t automatically bad. We’d simply use it soon and expect it to be firmer than a fresh bag.

How Long Does Marshmallow Creme Last?

Marshmallow creme is the shorter-lived product. The charts we read put it at 2 to 5 months unopened. NDSU gives 1 month once opened, with the note to cover it tightly and serve it at room temperature.

The charts differ on the refrigerator. K-State, New Mexico State, the Idaho, Oregon State and Washington State chart, Texas A&M and Ohio State all say to refrigerate creme after opening. The K-State, Idaho and Ohio State wording is “to extend storage life.” NDSU doesn’t say to refrigerate it. Marshmallow Fluff’s FAQ says Fluff can be stored at room temperature and that refrigeration will extend the shelf life significantly. It gives no numeric storage time.

So follow the label on your jar. We found no agency rule for how long an opened jar can safely sit out, and the charts frame refrigeration as extending storage life. We’d refrigerate an opened jar, which both the charts and Fluff’s maker say helps, and use it within about a month.

Do Homemade Marshmallows Go Bad?

Yes, and they have no single storage time. We found no extension or agency figure, and the commercial charts above don’t apply to a homemade recipe. Follow the storage instructions for the recipe you used, keep them in a tightly closed container, and discard any with mold.

Why Do Marshmallows Get Hard or Sticky?

We found no extension source that explains it, so this is our reading rather than an agency finding. Hardening and clumping are texture changes, not mold. The charts that add a note say to keep marshmallows in an airtight container, and K-State advises keeping them away from heat sources such as appliances and sunlight. We’d keep them away from steam and humidity too. None of the guides we read treats a firm marshmallow as unsafe on its own.

Clemson Extension’s water activity article describes water activity as the water available for microbial growth, on a scale from 0 to 1.0. In a general table, it lists marshmallows in the 0.75 band and lists some molds among the organisms that can grow there. It says drying to below 0.60 keeps microorganisms from growing, and that foods with the same water content can have very different water activities. The table isn’t a measurement of any particular bag, but it is why marshmallows aren’t necessarily mold-proof.

Can You Freeze Marshmallows?

Many food sites say marshmallows freeze well. The extension guides we read give no marshmallow-specific freezer time, so we can’t give one, and the pantry estimates above shouldn’t be treated as freezer estimates. Follow the manufacturer’s guidance where it exists.

How Do You Soften Hard Marshmallows?

We found no extension guidance on softening them. Prevention is what the charts point to, which means an airtight container. For recipes where a soft, smooth result matters, we’d use fresh marshmallows.

How Can You Tell If Marshmallows Are Bad?

We found no agency list of spoiled-marshmallow signs, so this checklist is partly our own. A normal look or smell doesn’t prove safety. The Idaho, Oregon State and Washington State publication says the presence of pathogens cannot always be detected by appearance or smell.

USDA’s page on mold on food says that if food is covered with mold, discard it, and it says not to sniff the moldy item because it can cause respiratory trouble. USDA’s table doesn’t list candy, but it says porous foods like bread and baked goods can be contaminated below the surface. Marshmallows are soft and airy, so we’d discard a moldy one rather than scrape it.

UC IPM’s pantry pest page says webbing in tight places of a package or tiny holes in a food container are signs of a pantry pest infestation. It says Indian meal moth larvae attack a range of products, including chocolate, candies and other confections. It says to throw away any food with evidence of infestation, to inspect packages, especially opened ones, and to store food in containers with tight-fitting lids rather than plastic bags.

Beyond those, we’d also toss marshmallows that smell sour or fermented when you open the bag, or that have turned wet and slimy. We don’t suggest tasting to test.

Can Old Marshmallows Make You Sick?

We found no agency data on illness from marshmallows specifically, so we can’t give a risk figure. Age and a Best By date alone don’t establish that a bag is unsafe, but storage conditions, package damage, mold and pests all matter. USDA’s mold page says that in dangerous molds, toxins are often contained in and around the mold’s root threads, and it says to discard food covered with mold. This is general information, not medical advice.

How Should You Store Marshmallows?

Airtight, cool and dry. The extension charts that add a note say to keep marshmallows in an airtight container, and K-State recommends a cool, dry, dark spot away from heat sources. We’d reseal the bag after each use, keep it away from the stove and any steam, and write the date you opened it on the bag. For a jar of marshmallow creme, cover it tightly and follow the label on refrigeration.

Our guide on how to store leftover Halloween candy covers the rest of the candy stash.

What Else Goes With Marshmallows?

Marshmallows rarely travel alone, and the other ingredients have their own clocks. For hot drinks, see our hot chocolate recipes, dark hot chocolate and whether cocoa powder goes bad. For s’mores, check whether chocolate goes bad. Making treats from scratch? See whether sugar goes bad and whether corn syrup goes bad.

On the holiday table, marshmallows top sweet potato casseroles, so see whether you can freeze sweet potatoes too. Looking for a fun use? Try our toasted marshmallow shot glass and fall popcorn bark. For other toppings, see whether whipped cream goes bad and whether Cool Whip goes bad.

Do Marshmallows Go Bad FAQ

Do marshmallows go bad?

Yes, slowly. Extension charts put pantry storage at 2 to 3 months up to 1 year, and NDSU gives 1 month once opened. Discard marshmallows with mold or signs of insects.

See also

Food Storage

Does Bisquick Go Bad or Expire? Everything You Should Know

Further Reading

• Does Hot Cocoa Mix Go Bad?
• Food Storage Guide