It's the almost same declension pattern as all adjectives, words mój, nasz, żaden etc. and similar to ten, jeden etc.

The only points where those similar patterns may differ is in singular: nominative/vocative masculine (it's usually -y/i, but sometimes nothing or -en), nominative/accusative/vocative neuter (usually -e, in few cases -o) and accusative feminine (always -ą, except for tę). All the other endings in singular and all endings in plural always follow the same pattern.

Also, you can see traces of adjectival declension in the declensions of words like on, ona, ono, oni, one, kto, co.