Why one chestnut won't trouble a growing kitten
At 2 kg, your kitten's digestive system is still developing, but a single cooked, peeled chestnut is too small to cause harm. Unlike adult cats, kittens are more prone to minor stomach upsets from new foods, but chestnuts lack the high fat or toxic compounds found in other nuts. The biggest risk here isn't the nut itself—it's whether she might have grabbed something else off the floor along with it.
Watch for any gagging or exaggerated swallowing, which would suggest the nut was gulped down too fast rather than chewed. Kittens this age often play with food before eating it, so if she seemed to chew it normally, you're even less likely to see issues. Soft stool or a single loose bowel movement could happen simply because it's a new food, not because it's dangerous.
The next 12 hours with a 10-week-old kitten
Kittens process foods faster than adult cats, so any reaction would show within 6–8 hours if it were going to. Since chestnuts aren't irritating or toxic, you're watching for mechanical issues like choking (unlikely now) or mild digestive novelty. Her energy levels and appetite should stay completely normal—if she acts sleepy or refuses her next meal, that would be unusual and worth a vet call.
Baby cats often investigate textures with their mouths, so this might have been more about play than hunger. Ensure she has appropriate toys to redirect this behavior. If she seeks out more chestnuts, it's safe to give another half of one as an occasional treat, but don't make it routine—kittens need protein-rich foods for growth.
When chestnuts become risky for small pets
The danger would come from quantity, not quality: if your kitten ate 4–5 chestnuts in one sitting, the fiber and carbs could overwhelm her little gut. Cooked nuts also expand slightly in the stomach, so bulk matters more than toxicity. What you've described is equivalent to a human toddler eating one grape—noticeable but not concerning.
Never offer raw chestnuts, which contain tannins that can cause stomach irritation, or any nuts in shells. Salted or seasoned chestnuts are also off-limits—the sodium and spices could bother her more than the nut itself. Plain, cooked, and peeled is the only safe form for cats of any size.
Kitten-specific quirks with new foods
At 10 weeks, kittens are still learning what's edible, so they may react to unfamiliar textures. Some will smack their lips or shake their heads after tasting something new—this doesn't mean it's harmful, just unexpected. If your kitten did this and then walked away, she was probably commenting on the chestnut's mild sweetness rather than having a bad reaction.
Monitor her litter box for the next day. Perfectly normal stool means she handled it fine; slightly loose (but still formed) stool suggests her gut noticed the change but wasn't distressed. True diarrhea—watery, frequent, or urgent—would be surprising from this small amount and might signal she ate something else you didn't see.
The full verdict, portion guidance and serving notes are collected on the Chestnuts food facts page.