10% more Sp. Defense and 10% less Sp. Attack. Careful suits Pokemon that rely on physical attacks or status moves while tanking special hits. Over in Crystal, Ho-Oh is one of the most popular Careful users, alongside Skarmory and Snorlax. There's no way to set natures in Crystal. You'll lock in Careful when catching or breeding in Ruby/Sapphire or later.

Careful raises Sp. Defense by 10% and lowers Sp. Attack by 10%. Special walls that rely on physical or status moves. 59 Pokemon competitively run this nature.
#PokemonTierRoleAbility+SpD-SpASpe
1
Ho-Oh
Ho-Oh
FIREFLYING
SBulky SupportRegenerator
154+20
110-13
90
2
Skarmory
Skarmory
STEELFLYING
ABulky SupportKeeneye
70+12
40-6
70
3
Snorlax
Snorlax
NORMAL
ABulky SupportThickfat
110+16
65-9
30
4
Clefable
Clefable
FAIRY
ABulky SupportMagic Guard
90+14
95-12
60
5
Mew
Mew
PSYCHIC
ABulky SupportSynchronize
100+15
100-12
100
6
Gyarados
Gyarados
WATERFLYING
ABulky SupportIntimidate
100+15
60-8
81
7
Hitmontop
Hitmontop
FIGHTING
ABulky SupportIntimidate
110+16
35-6
70
8
Rhydon
Rhydon
GROUNDROCK
ABulky SupportLightningrod
45+9
45-7
40
9
Sandslash
Sandslash
GROUND
ABulky SupportSandrush
55+10
45-7
65
Ho-Oh
Ho-Oh
FIRE FLYING
S
Role
Bulky Support
Ability
Regenerator
+SpD
154 +20
Spe
90
Skarmory
Skarmory
STEEL FLYING
A
Role
Bulky Support
Ability
Keeneye
+SpD
70 +12
Spe
70
Snorlax
Snorlax
NORMAL
A
Role
Bulky Support
Ability
Thickfat
+SpD
110 +16
Spe
30
Clefable
Clefable
FAIRY
A
Role
Bulky Support
Ability
Magic Guard
+SpD
90 +14
Spe
60
Mew
Mew
PSYCHIC
A
Role
Bulky Support
Ability
Synchronize
+SpD
100 +15
Spe
100
Gyarados
Gyarados
WATER FLYING
A
Role
Bulky Support
Ability
Intimidate
+SpD
100 +15
Spe
81
Hitmontop
Hitmontop
FIGHTING
A
Role
Bulky Support
Ability
Intimidate
+SpD
110 +16
Spe
70
Rhydon
Rhydon
GROUND ROCK
A
Role
Bulky Support
Ability
Lightningrod
+SpD
45 +9
Spe
40
Sandslash
Sandslash
GROUND
A
Role
Bulky Support
Ability
Sandrush
+SpD
55 +10
Spe
65
+10%Sp. Defense
-10%Sp. Attack
Flavor Preference
Likes Bitter, dislikes Dry
Competitive Role
Special walls that rely on physical or status moves.
Careful vs Calm
Choose Careful
+Sp. Defense / -Sp. Attack
  • Pokemon that need to check physical threats (use +Def)
  • Pokemon that need to check special threats (use +SpD)
  • Walls and tanks that rarely attack
Choose Calm
+Sp. Defense / -Attack
  • Defensive Pokemon that still need attacking power
  • Pokemon that run both physical and special moves
How to Get
SynchronizeLead with a Careful Pokemon that has the Synchronize ability. Wild Pokemon will match its nature. (Gen 3+)
BreedingGive the parent with Careful nature an Everstone. The offspring will inherit it. (100% since Gen 5)
Nature MintUse a Careful Mint to change stat effects to Careful. The original nature name stays but stats change. (Gen 8+)
Other +Sp. Defense Natures
Calm (-Attack)Gentle (-Defense)Sassy (-Speed)
What does the Careful nature do in Pokemon?
Careful gives your Pokemon 10% more Sp. Defense at the cost of Sp. Attack. That tradeoff works best when the lowered stat isn't part of your moveset. Pokemon with Careful nature prefer Bitter flavor and dislike Dry.
What are the best Careful nature Pokemon?
Competitively, Ho-Oh, Skarmory, Snorlax, and Clefable run Careful most often. The +Sp. Defense boost complements their role, and the -Sp. Attack penalty barely affects their game plan.
Is Careful a good nature for competitive Pokemon?
For the right Pokemon, Careful is one of the best natures you can pick. It fills a solid niche for defensive builds. Just don't slap it on something that uses Sp. Attack-based moves.
How do I get a Careful nature Pokemon?
Breeding with an Everstone is the most reliable approach since Gen 5. The parent holding it passes its nature to every offspring. Synchronize works for wild catches. And if you already have the Pokemon, a Careful Mint from the Battle Tower changes the stat effects to Careful.
Should I use Careful or Calm?
Short answer: Careful for physical wall utility, Calm for special wall utility. There's no universal best. Check your Pokemon's base stats and common threats in the format you're playing to decide which tradeoff is better.