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?
The Short Answer: Yes, but slowly. University extension charts put pantry storage anywhere from 2 to 3 months up to 1 year, and several don’t say whether that is for opened or unopened marshmallows. NDSU lists 1 year unopened and 1 month opened. Hardness or clumping on its own is a quality change, but discard marshmallows with mold or signs of insects. For marshmallow creme, follow the jar’s label. Most charts say to refrigerate it after opening, while the maker of Marshmallow Fluff says room temperature is fine and refrigeration extends shelf life.
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.
Do Marshmallows Go Bad: At a Glance
Marshmallows, pantry
2 to 3 months up to 1 year, depending on the extension chart. NDSU: 1 year unopened
Opened marshmallows
NDSU: 1 month, in an airtight container. Other charts do not separate opened from unopened
Unopened marshmallow creme
2 to 5 months across the extension charts we read
Opened marshmallow creme
Follow the jar’s label. Most charts say refrigerate. Fluff’s maker says room temperature is fine
Homemade marshmallows
No universal time. Follow your recipe’s storage instructions
Freezer
The guides we read give no marshmallow freezer time
Where to keep them
A cool, dry, dark spot away from heat, per K-State
Signs to toss
Mold, insects, webbing or tiny holes in the package. Hardness alone is a quality change
Safety
We don’t suggest tasting to test, and USDA says not to sniff moldy food
Key Takeaways
Published pantry-storage estimates for marshmallows range from 2 to 3 months up to 1 year. NDSU and New Mexico State say 1 year unopened, and K-State lists 1 year. Other charts give 2 to 4 months or 2 to 3.
Several charts don’t say whether their figure is for opened or unopened marshmallows. NDSU is the only one we found that gives a figure once opened, at 1 month.
These are best-quality estimates, not safety deadlines. The Idaho, Oregon State and Washington State publication says storage times depend on temperature, humidity, packaging and the food itself.
Marshmallow creme runs 2 to 5 months unopened. Most charts say to refrigerate it after opening to extend storage life, and Marshmallow Fluff’s maker says refrigeration extends shelf life significantly.
NDSU’s April 2013 edition gave marshmallows 2 to 3 months, and its current guide gives 1 year, which helps explain why you see both numbers.
Marshmallows are not necessarily mold-proof. Clemson Extension lists them in a general table at a water activity of 0.75, above the 0.60 level below which microo
