Can hamsters eat cucumber?

Yes — safe in normal portions

Yes. Cucumber is a safe, low-sugar vegetable and a good treat for dwarf hamsters, but it is mostly water, so keep portions small to avoid loose droppings.

Portion: A piece about 1–1.5 cm (⅜–⅝ in) across for a Syrian; about half that for a dwarf. Keep all fresh food together to about 1–2 teaspoons a day for a Syrian and about half that for a dwarf.
How often: A few times a week, rotated with other vegetables.
Sugar: 1.7 g / 100 g

How to serve it

Wash well
Cut a small piece; washed skin can stay on
Serve raw
Remove any uneaten piece, including from the hoard, within a few hours

Why

Risks. Cucumber is mostly water with little nutrition, so large amounts can cause diarrhoea. Hoarded pieces go off quickly in the bedding.

Benefits. Very low in sugar and calories, which makes it a sensible treat for diabetes-prone dwarf hamsters.

Questions owners ask 2

Can hamsters eat cucumber skin?

Yes, if it is washed well. Peel it if you cannot wash off a waxy coating.

Can cucumber replace my hamster's water?

No. Fresh water should always be available in a clean bottle or bowl, changed daily.

Cucumber: nutrition per 100 g

Water	95.2 g
Energy	15 kcal
Sugars	1.7 g
Fat	0.1 g
Protein	0.7 g
Fibre	0.5 g
Calcium	16 mg
Phosphorus	24 mg
Calcium : phosphorus	0.67 : 1
Sodium	2 mg
Vitamin A (RAE)	5 µg
Vitamin C	2.8 mg

“Cucumber, with peel, raw”, USDA FoodData Central (SR Legacy, FDC 168409). Public domain.

Sources & method 6

The sources below discuss cucumber for hamsters (or for pet rodents generally). Confidence: high. Rated on the JOMIZOO Feeding Scale; when good sources disagree we choose the more cautious level.

What to feed your hamster - safe foods, fruit, veg and a complete feeding guide — Woodgreen Pets Charity
Hamsters as pets — PDSA
Hamster Care Sheet — UC Davis Veterinary Medical Teaching Hospital, Companion Avian and Exotic Pet Medicine and Surgery Service (PDF hosted by Wise Owl Animal Hospital)
Dwarf Hamster Care Sheet — PetMD (written by Maria Zayas, DVM; reviewed by Melissa Witherell, DVM)
What Can Hamsters Eat? — PetMD (written by Angelina Childree, LVT; reviewed by Melissa Witherell, DVM)
Can Hamsters Eat Broccoli & What to Feed Your Hamster — Northgate Veterinary Clinic, Seattle