Whether you’re meticulously assembling the nursery before the big arrival or you’re approaching that six-month milestone when your baby is ready for their own sleeping quarters, choosing the best mattress for your cot is essential for a proper night’s sleep.
Cot mattresses generally come in two standard sizes: 120cm x 60cm for a traditional cot, and 140cm x 70cm for a cot bed. Choosing the correct size is key, as a mattress that doesn’t fit properly can pose a safety risk.
The experts at children’s charity The Lullaby Trust advise that your cot mattress is firm, flat, and fits snugly in the cot – ideally with no gaps around the edges, or at most, no more than 1cm.
While a plush, pillow-soft mattress might seem appealing, babies actually need a firmer sleep surface to support safer sleep and help regulate temperature. The charity advises that when your baby is lying on the mattress, their head should sink by no more than a few millimetres.
It’s also worth considering a waterproof design or a mattress with a removable waterproof cover. Alongside making inevitable spills and leaks easier to deal with, this helps stop moisture and bacteria from building up inside the mattress, keeping your baby’s sleep space fresher and more hygienic.
Read more: Best cot beds for babies and toddlers that offer a long-term sleep solution
The best cot mattresses for 2026 are:
- Best overall – Mother&Baby pure gold anti-allergy coir pocket sprung cot bed mattress: £129.99, Boots.com
- Best budget buy – Mamas & Papas essential fibre cotbed mattress: £41.04, Babyplanetonline.co.uk
- Best for older babies and toddlers – The Tiny Bed Company tiny dreamer deluxe organic coconut and pocket sprung cot bed mattress: £189.95, Thetinybedcompany.com
- Best for travel – Ickle Bubba fibre cot mattress: £69, Icklebubba.com
Read more: The best nursery furniture brands in 2026