What does the Careful nature do?

Careful raises Sp. Def by 10% and lowers Sp. Atk by 10%.

What stat does Careful increase?

Careful increases Sp. Def by 10% and decreases Sp. Atk by 10%. HP is unaffected.

A Careful Pokémon likes Bitter flavors (tied to Sp. Def) and dislikes Dry flavors (tied to Sp. Atk).

Yes. Use a Careful Mint to apply the Careful stat effect to any Pokémon without changing its displayed nature.

Nature

Raises Sp. Def, lowers Sp. Atk.

Raises Sp. Def +10%

Lowers Sp. Atk −10%

LikesBitter

DislikesDry

Special walls and bulky physical attackers. A top defensive nature.

Calm −Attack Gentle −Defense Sassy −Speed

What does the Careful nature do?: Careful raises Sp. Def by 10% and lowers Sp. Atk by 10%.
What stat does Careful increase?: Careful increases Sp. Def by 10% and decreases Sp. Atk by 10%. HP is unaffected.
What flavor does a Careful Pokémon like?: A Careful Pokémon likes Bitter flavors (tied to Sp. Def) and dislikes Dry flavors (tied to Sp. Atk).
Can I change a Pokémon to Careful?: Yes. Use a Careful Mint to apply the Careful stat effect to any Pokémon without changing its displayed nature.