Natures

Each individual Pokémon has a Nature that influences its stats. This Nature is randomly determined upon encountering the Pokémon and cannot be changed. Each Nature raises one stat by 10% and decreases another stat by 10%. No Natures influence HP, and certain Natures don't affect stats at all.

Nature Increased stat Decreased stat
Adamant Attack Special Attack
Bashful None None
Bold Defense Attack
Brave Attack Speed
Calm Special Defense Attack
Careful Special Defense Special Attack
Docile None None
Gentle Special Defense Defense
Hardy None None
Hasty Speed Defense
Impish Defense Special Attack
Jolly Speed Special Attack
Lax Defense Special Defense
Lonely Attack Defense
Mild Special Attack Defense
Modest Special Attack Attack
Naive Speed Special Defense
Naughty Attack Special Defense
Quiet Special Attack Speed
Quirky None None
Rash Special Attack Special Defense
Relaxed Defense Speed
Sassy Special Defense Speed
Serious None None
Timid Speed Attack

IDs

Within NBT tags, Natures are stored as numerical IDs. These numbers are only useful when editing Pokémon NBT data externally.

Nature ID
Adamant 7
Bashful 3
Bold 9
Brave 6
Calm 21
Careful 24
Docile 2
Gentle 22
Hardy 0
Hasty 14
Impish 11
Jolly 15
Lax 12
Lonely 5
Mild 18
Modest 17
Naive 16
Naughty 8
Quiet 19
Quirky 4
Rash 20
Relaxed 10
Sassy 23
Serious 1
Timid 13