Serious keeps every stat at 1x. No boost, no drop. That might sound safe, but you're giving up a free 10% in the stat that matters most. Nature Mints (Gen 8+) make it easy to fix. Legends: Arceus assigns natures at random. There's no way to target or change Serious, but you wouldn't want to anyway.
Serious is a neutral nature with no stat change. For speed pokemon, use Jolly or Timid instead.
Jolly
+Speed/-Sp. Attack
Max Speed for physical attackers
Timid
+Speed/-Attack
Max Speed for special attackers
| # | Pokemon | Nature | Tier | Role | Ability | Spe |
|---|---|---|---|---|---|---|
| 1 |  Garchomp DRAGONGROUND | Jolly | S | Physical Attacker | Rough Skin | 102 |
| 2 |  Landorus GROUND | Timid | S | Utility | Sheerforce | 101 |
| 3 | Timid | S | Special Attacker | Prankster | 111 | |
| 4 |  Sneasler FIGHTINGPOISON | Jolly | S | Physical Attacker | Unburden | 120 |
| 5 |  Gengar GHOSTPOISON | Timid | A | Special Attacker | Levitate | 110 |
| 6 |  Heatran FIRESTEEL | Timid | A | Special Attacker | Flashfire | 77 |
| 7 |  Elekid ELECTRIC | Timid | A | Special Attacker | Vitalspirit | 95 |
| 8 |  Jolteon ELECTRIC | Timid | A | Special Attacker | Voltabsorb | 130 |
| 9 |  Espeon PSYCHIC | Timid | A | Special Attacker | Magic Bounce | 110 |
| 10 |  Weavile DARKICE | Jolly | A | Physical Attacker | Pressure | 125 |
| 11 |  Ambipom NORMAL | Jolly | A | Physical Attacker | Technician | 115 |
| 12 |  Arcanine FIRE | Jolly | A | Physical Attacker | Intimidate | 95 |
| 13 |  Goodra DRAGON | Timid | A | Special Attacker | Sapsipper | 80 |
| 14 |  Ninetales FIRE | Timid | B | Special Attacker | Flashfire | 100 |
| 15 |  Skuntank POISONDARK | Jolly | B | Bulky Support | Aftermath | 84 |
| 16 |  Infernape FIREFIGHTING | Jolly | B | Physical Attacker | Blaze | 108 |
| 17 |  Stunky POISONDARK | Jolly | B | Physical Attacker | Aftermath | 74 |
| 18 |  Azelf PSYCHIC | Jolly | B | Bulky Support | Levitate | 115 |
| 19 |  Alakazam PSYCHIC | Timid | B | Special Attacker | Magic Guard | 120 |
| 20 |  Togekiss FAIRY | Timid | B | Special Attacker | Serenegrace | 80 |
Serious is a neutral nature — no stat is increased or decreased.
Competitive Role
No competitive advantage. A stat-boosting nature is almost always preferred.
How to Get
SynchronizeLead with a Serious Pokemon that has the Synchronize ability. Wild Pokemon will match its nature. (Gen 3+)
BreedingGive the parent with Serious nature an Everstone. The offspring will inherit it. (100% since Gen 5)
Nature MintUse a Serious Mint to change stat effects to Serious. The original nature name stays but stats change. (Gen 8+)
Recommended Alternatives
What does the Serious nature do in Pokemon?
Nothing, basically. Serious doesn't change any stat. There's no boost and no penalty. Your Pokemon keeps its base stat spread exactly as-is.
Is Serious nature good?
There's no competitive reason to keep Serious. A 10% stat boost from any other nature is free power you're leaving on the table. Nature Mints (Gen 8+) let you change it without breeding.
How do I get a Serious nature Pokemon?
Catch a Pokemon and check. There's a 4% chance of any specific nature, including Serious. Synchronize ability matches the lead Pokemon's nature to wild encounters (Gen 3+). Everstone passes a parent's nature during breeding.
When should you use a neutral nature?
Almost never. The only edge case is a Pokemon that uses physical moves, special moves, and needs every defensive stat and Speed. That Pokemon doesn't really exist in competitive. Even mixed attackers prefer Naive, Hasty, or another nature that at least boosts Speed.