diff --git a/data/battle_scripts_1.s b/data/battle_scripts_1.s
index 4fae034bfe6b..fe278d14f6a7 100644
--- a/data/battle_scripts_1.s
+++ b/data/battle_scripts_1.s
@@ -8678,6 +8678,13 @@ BattleScript_CostarActivates::
 	waitmessage B_WAIT_TIME_LONG
 	end3
 
+BattleScript_ZeroToHeroActivates::
+	pause B_WAIT_TIME_SHORT
+	call BattleScript_AbilityPopUp
+	printstring STRINGID_ZEROTOHEROTRANSFORMATION
+	waitmessage B_WAIT_TIME_LONG
+	end3
+
 BattleScript_AttackWeakenedByStrongWinds::
 	pause B_WAIT_TIME_SHORT
 	printstring STRINGID_ATTACKWEAKENEDBSTRONGWINDS
diff --git a/include/battle.h b/include/battle.h
index 04db26bf4a39..350a313d939b 100644
--- a/include/battle.h
+++ b/include/battle.h
@@ -700,7 +700,7 @@ struct BattleStruct
     bool8 effectsBeforeUsingMoveDone:1; // Mega Evo and Focus Punch/Shell Trap effects.
     u8 targetsDone[MAX_BATTLERS_COUNT]; // Each battler as a bit.
     u16 overwrittenAbilities[MAX_BATTLERS_COUNT];    // abilities overwritten during battle (keep separate from battle history in case of switching)
-    bool8 allowedToChangeFormInWeather[PARTY_SIZE][2]; // For each party member and side, used by Ice Face.
+    bool8 allowedToChangeFormInWeather[PARTY_SIZE][NUM_BATTLE_SIDES]; // For each party member and side, used by Ice Face.
     u8 battleBondTransformed[NUM_BATTLE_SIDES]; // Bitfield for each party.
     u8 storedHealingWish:4; // Each battler as a bit.
     u8 storedLunarDance:4; // Each battler as a bit.
@@ -718,6 +718,7 @@ struct BattleStruct
     bool8 trainerSlideBeforeFirstTurnMsgDone;
     u32 aiDelayTimer; // Counts number of frames AI takes to choose an action.
     u32 aiDelayFrames; // Number of frames it took to choose an action.
+    bool8 transformZeroToHero[PARTY_SIZE][NUM_BATTLE_SIDES];
 };
 
 // The palaceFlags member of struct BattleStruct contains 1 flag per move to indicate which moves the AI should consider,
diff --git a/include/battle_scripts.h b/include/battle_scripts.h
index bdcf1081b9d1..d2addbc4c33b 100644
--- a/include/battle_scripts.h
+++ b/include/battle_scripts.h
@@ -459,6 +459,7 @@ extern const u8 BattleScript_RuinAbilityActivates[];
 extern const u8 BattleScript_CudChewActivates[];
 extern const u8 BattleScript_SupremeOverlordActivates[];
 extern const u8 BattleScript_CostarActivates[];
+extern const u8 BattleScript_ZeroToHeroActivates[];
 extern const u8 BattleScript_ToxicDebrisActivates[];
 extern const u8 BattleScript_EarthEaterActivates[];
 extern const u8 BattleScript_MimicryActivates_End3[];
diff --git a/include/constants/battle_string_ids.h b/include/constants/battle_string_ids.h
index a9a6b7025b01..69e3dd935dd3 100644
--- a/include/constants/battle_string_ids.h
+++ b/include/constants/battle_string_ids.h
@@ -685,8 +685,9 @@
 #define STRINGID_TEAMSURROUNDEDBYROCKS                683
 #define STRINGID_PKMNHURTBYROCKSTHROWN                684
 #define STRINGID_MOVEBLOCKEDBYDYNAMAX                 685
+#define STRINGID_ZEROTOHEROTRANSFORMATION             686
 
-#define BATTLESTRINGS_COUNT                           686
+#define BATTLESTRINGS_COUNT                           687
 
 // This is the string id that gBattleStringsTable starts with.
 // String ids before this (e.g. STRINGID_INTROMSG) are not in the table,
diff --git a/src/battle_message.c b/src/battle_message.c
index e6e87186b48a..f2052e691925 100644
--- a/src/battle_message.c
+++ b/src/battle_message.c
@@ -822,9 +822,11 @@ static const u8 sText_TargetIsBeingSaltCured[] = _("{B_DEF_NAME_WITH_PREFIX} is
 static const u8 sText_TargetIsHurtBySaltCure[] = _("{B_DEF_NAME_WITH_PREFIX} is hurt by {B_BUFF1}!");
 static const u8 sText_OpportunistCopied[] = _("{B_SCR_ACTIVE_NAME_WITH_PREFIX} copied its\nopponent's stat changes!");
 static const u8 sText_TargetCoveredInStickyCandySyrup[] = _("{B_DEF_NAME_WITH_PREFIX} got covered\nin sticky syrup!");
+static const u8 sText_ZeroToHeroTransformation[] = _("{B_ATK_NAME_WITH_PREFIX} underwent a heroic\ntransformation!");
 
 const u8 *const gBattleStringsTable[BATTLESTRINGS_COUNT] =
 {
+    [STRINGID_ZEROTOHEROTRANSFORMATION - BATTLESTRINGS_TABLE_START] = sText_ZeroToHeroTransformation,
     [STRINGID_MOVEBLOCKEDBYDYNAMAX - BATTLESTRINGS_TABLE_START] = sText_MoveBlockedByDynamax,
     [STRINGID_OPPORTUNISTCOPIED - BATTLESTRINGS_TABLE_START] = sText_OpportunistCopied,
     [STRINGID_TARGETISHURTBYSALTCURE - BATTLESTRINGS_TABLE_START] = sText_TargetIsHurtBySaltCure,
diff --git a/src/battle_script_commands.c b/src/battle_script_commands.c
index 34b861a6d48b..d5bdbaedae1f 100644
--- a/src/battle_script_commands.c
+++ b/src/battle_script_commands.c
@@ -9151,6 +9151,7 @@ static void Cmd_various(void)
             case ABILITY_SCHOOLING:         case ABILITY_COMATOSE:
             case ABILITY_SHIELDS_DOWN:      case ABILITY_DISGUISE:
             case ABILITY_RKS_SYSTEM:        case ABILITY_TRACE:
+            case ABILITY_ZERO_TO_HERO:
                 break;
             default:
                 gBattleStruct->tracedAbility[gBattlerAbility] = gBattleMons[battler].ability; // re-using the variable for trace
diff --git a/src/battle_util.c b/src/battle_util.c
index abd5f6ac20a9..2be621be553f 100644
--- a/src/battle_util.c
+++ b/src/battle_util.c
@@ -113,6 +113,7 @@ static const u16 sSkillSwapBannedAbilities[] =
     ABILITY_ICE_FACE,
     ABILITY_HUNGER_SWITCH,
     ABILITY_GULP_MISSILE,
+    ABILITY_ZERO_TO_HERO,
 };
 
 static const u16 sRolePlayBannedAbilities[] =
@@ -138,6 +139,7 @@ static const u16 sRolePlayBannedAbilities[] =
     ABILITY_ICE_FACE,
     ABILITY_HUNGER_SWITCH,
     ABILITY_GULP_MISSILE,
+    ABILITY_ZERO_TO_HERO,
 };
 
 static const u16 sRolePlayBannedAttackerAbilities[] =
@@ -154,6 +156,7 @@ static const u16 sRolePlayBannedAttackerAbilities[] =
     ABILITY_POWER_CONSTRUCT,
     ABILITY_ICE_FACE,
     ABILITY_GULP_MISSILE,
+    ABILITY_ZERO_TO_HERO,
 };
 
 static const u16 sWorrySeedBannedAbilities[] =
@@ -170,6 +173,7 @@ static const u16 sWorrySeedBannedAbilities[] =
     ABILITY_TRUANT,
     ABILITY_ICE_FACE,
     ABILITY_GULP_MISSILE,
+    ABILITY_ZERO_TO_HERO,
 };
 
 static const u16 sGastroAcidBannedAbilities[] =
@@ -188,6 +192,7 @@ static const u16 sGastroAcidBannedAbilities[] =
     ABILITY_SHIELDS_DOWN,
     ABILITY_STANCE_CHANGE,
     ABILITY_ZEN_MODE,
+    ABILITY_ZERO_TO_HERO,
 };
 
 static const u16 sEntrainmentBannedAttackerAbilities[] =
@@ -206,6 +211,7 @@ static const u16 sEntrainmentBannedAttackerAbilities[] =
     ABILITY_ICE_FACE,
     ABILITY_HUNGER_SWITCH,
     ABILITY_GULP_MISSILE,
+    ABILITY_ZERO_TO_HERO,
 };
 
 static const u16 sEntrainmentTargetSimpleBeamBannedAbilities[] =
@@ -221,6 +227,7 @@ static const u16 sEntrainmentTargetSimpleBeamBannedAbilities[] =
     ABILITY_BATTLE_BOND,
     ABILITY_ICE_FACE,
     ABILITY_GULP_MISSILE,
+    ABILITY_ZERO_TO_HERO,
 };
 
 static u8 CalcBeatUpPower(void)
@@ -994,6 +1001,7 @@ static const u8 sAbilitiesNotTraced[ABILITIES_COUNT] =
     [ABILITY_STANCE_CHANGE] = 1,
     [ABILITY_TRACE] = 1,
     [ABILITY_ZEN_MODE] = 1,
+    [ABILITY_ZERO_TO_HERO] = 1,
 };
 
 static const u8 sHoldEffectToType[][2] =
@@ -4695,6 +4703,17 @@ u32 AbilityBattleEffects(u32 caseID, u32 battler, u32 ability, u32 special, u32
                 effect++;
             }
             break;
+        case ABILITY_ZERO_TO_HERO:
+            if (!gSpecialStatuses[battler].switchInAbilityDone
+             && gBattleMons[battler].species == SPECIES_PALAFIN_HERO
+             && !gBattleStruct->transformZeroToHero[gBattlerPartyIndexes[battler]][GetBattlerSide(battler)])
+            {
+                gSpecialStatuses[battler].switchInAbilityDone = TRUE;
+                gBattleStruct->transformZeroToHero[gBattlerPartyIndexes[battler]][GetBattlerSide(battler)] = TRUE;
+                BattleScriptPushCursorAndCallback(BattleScript_ZeroToHeroActivates);
+                effect++;
+            }
+            break;
         }
         break;
     case ABILITYEFFECT_ENDTURN: // 1
@@ -6078,6 +6097,7 @@ bool32 IsNeutralizingGasBannedAbility(u32 ability)
     case ABILITY_ICE_FACE:
     case ABILITY_AS_ONE_ICE_RIDER:
     case ABILITY_AS_ONE_SHADOW_RIDER:
+    case ABILITY_ZERO_TO_HERO:
         return TRUE;
     default:
         return FALSE;
diff --git a/src/data/pokemon/form_change_table_pointers.h b/src/data/pokemon/form_change_table_pointers.h
index 211078837309..c3f67ce3c882 100644
--- a/src/data/pokemon/form_change_table_pointers.h
+++ b/src/data/pokemon/form_change_table_pointers.h
@@ -355,6 +355,8 @@ const struct FormChange *const gFormChangeTablePointers[NUM_SPECIES] =
     [SPECIES_ENAMORUS_THERIAN] = sEnamorusFormChangeTable,
 #endif
 #if P_GEN_9_POKEMON == TRUE
+    [SPECIES_PALAFIN_ZERO] = sPalafinZeroFormChangeTable,
+    [SPECIES_PALAFIN_HERO] = sPalafinZeroFormChangeTable,
     [SPECIES_OGERPON_TEAL_MASK] = sOgerponFormChangeTable,
     [SPECIES_OGERPON_WELLSPRING_MASK] = sOgerponFormChangeTable,
     [SPECIES_OGERPON_HEARTHFLAME_MASK] = sOgerponFormChangeTable,
diff --git a/src/data/pokemon/form_change_tables.h b/src/data/pokemon/form_change_tables.h
index 2dcadabd3673..012e1350f233 100644
--- a/src/data/pokemon/form_change_tables.h
+++ b/src/data/pokemon/form_change_tables.h
@@ -800,6 +800,12 @@ static const struct FormChange sUrshifuRapidStrikeFormChangeTable[] =
     {FORM_CHANGE_TERMINATOR},
 };
 
+static const struct FormChange sPalafinZeroFormChangeTable[] =
+{
+    {FORM_CHANGE_BATTLE_SWITCH, SPECIES_PALAFIN_HERO},
+    {FORM_CHANGE_TERMINATOR},
+};
+
 #endif
 
 #undef WHEN_LEARNED
diff --git a/test/battle/ability/zero_to_hero.c b/test/battle/ability/zero_to_hero.c
new file mode 100644
index 000000000000..4b9184cecae7
--- /dev/null
+++ b/test/battle/ability/zero_to_hero.c
@@ -0,0 +1,140 @@
+#include "global.h"
+#include "test/battle.h"
+
+ASSUMPTIONS
+{
+    ASSUME(P_GEN_9_POKEMON == TRUE);
+}
+
+SINGLE_BATTLE_TEST("Zero to Hero transforms Palafin when it switches out")
+{
+    GIVEN {
+        PLAYER(SPECIES_PALAFIN_ZERO) { Ability(ABILITY_ZERO_TO_HERO); }
+        PLAYER(SPECIES_WOBBUFFET);
+        OPPONENT(SPECIES_WOBBUFFET);
+    } WHEN {
+        TURN { SWITCH(player, 1); }
+        TURN { SWITCH(player, 0); }
+    } SCENE {
+        MESSAGE("Palafin, that's enough! Come back!");
+        MESSAGE("Go! Wobbuffet!");
+        MESSAGE("Wobbuffet, that's enough! Come back!");
+        MESSAGE("Go! Palafin!");
+        ABILITY_POPUP(player, ABILITY_ZERO_TO_HERO);
+        MESSAGE("Palafin underwent a heroic transformation!");
+    } THEN { EXPECT_EQ(player->species, SPECIES_PALAFIN_HERO); }
+}
+
+SINGLE_BATTLE_TEST("Zero to Hero can't be surpressed by Neutralizing Gas")
+{
+    GIVEN {
+        PLAYER(SPECIES_PALAFIN_ZERO) { Ability(ABILITY_ZERO_TO_HERO); }
+        PLAYER(SPECIES_WOBBUFFET);
+        OPPONENT(SPECIES_KOFFING) { Ability(ABILITY_NEUTRALIZING_GAS); }
+    } WHEN {
+        TURN { SWITCH(player, 1); }
+        TURN { SWITCH(player, 0); }
+    } SCENE {
+        ABILITY_POPUP(opponent, ABILITY_NEUTRALIZING_GAS);
+        ABILITY_POPUP(player, ABILITY_ZERO_TO_HERO);
+        MESSAGE("Palafin underwent a heroic transformation!");
+    } THEN { EXPECT_EQ(player->species, SPECIES_PALAFIN_HERO); }
+}
+
+SINGLE_BATTLE_TEST("Zero to Hero transforms both player and opponent")
+{
+    GIVEN {
+        PLAYER(SPECIES_PALAFIN_ZERO) { Ability(ABILITY_ZERO_TO_HERO); }
+        PLAYER(SPECIES_WOBBUFFET);
+        OPPONENT(SPECIES_PALAFIN_ZERO) { Ability(ABILITY_ZERO_TO_HERO); }
+        OPPONENT(SPECIES_WOBBUFFET);
+    } WHEN {
+        TURN { SWITCH(player, 1); SWITCH(opponent, 1); }
+        TURN { SWITCH(player, 0); SWITCH(opponent, 0); }
+    } SCENE {
+        ABILITY_POPUP(player, ABILITY_ZERO_TO_HERO);
+        MESSAGE("Palafin underwent a heroic transformation!");
+        ABILITY_POPUP(opponent, ABILITY_ZERO_TO_HERO);
+        MESSAGE("Foe Palafin underwent a heroic transformation!");
+    } THEN {
+        EXPECT_EQ(player->species, SPECIES_PALAFIN_HERO);
+        EXPECT_EQ(opponent->species, SPECIES_PALAFIN_HERO);
+        }
+}
+
+SINGLE_BATTLE_TEST("Zero to Hero will activate if a switch move is used")
+{
+    GIVEN {
+        ASSUME(gBattleMoves[MOVE_FLIP_TURN].effect == EFFECT_HIT_ESCAPE);
+        PLAYER(SPECIES_PALAFIN_ZERO) { Ability(ABILITY_ZERO_TO_HERO); }
+        PLAYER(SPECIES_WOBBUFFET);
+        OPPONENT(SPECIES_WOBBUFFET);
+    } WHEN {
+        TURN { MOVE(player, MOVE_FLIP_TURN); SEND_OUT(player, 1); }
+        TURN { SWITCH(player, 0); }
+    } SCENE {
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_FLIP_TURN, player);
+        ABILITY_POPUP(player, ABILITY_ZERO_TO_HERO);
+        MESSAGE("Palafin underwent a heroic transformation!");
+    } THEN { EXPECT_EQ(player->species, SPECIES_PALAFIN_HERO); }
+}
+
+SINGLE_BATTLE_TEST("Gastro Acid, Worry Seed, and Simple Beam fail if the target has the Ability Zero to Hero")
+{
+    u16 move;
+
+    PARAMETRIZE { move = MOVE_GASTRO_ACID; }
+    PARAMETRIZE { move = MOVE_WORRY_SEED; }
+    PARAMETRIZE { move = MOVE_SIMPLE_BEAM; }
+
+    GIVEN {
+        ASSUME(gBattleMoves[MOVE_GASTRO_ACID].effect == EFFECT_GASTRO_ACID);
+        ASSUME(gBattleMoves[MOVE_WORRY_SEED].effect == EFFECT_WORRY_SEED);
+        ASSUME(gBattleMoves[MOVE_SIMPLE_BEAM].effect == EFFECT_SIMPLE_BEAM);
+        PLAYER(SPECIES_PALAFIN_ZERO) { Ability(ABILITY_ZERO_TO_HERO); }
+        OPPONENT(SPECIES_WOBBUFFET);
+    } WHEN {
+        TURN { MOVE(opponent, move); }
+    } SCENE {
+        NOT ANIMATION(ANIM_TYPE_MOVE, move, player);
+        MESSAGE("But it failed!");
+    }
+}
+
+SINGLE_BATTLE_TEST("Role Play, Skill Swap, and Entrainment fail if either Pokémon has Zero to Hero")
+{
+    u16 move;
+
+    PARAMETRIZE { move = MOVE_ROLE_PLAY; }
+    PARAMETRIZE { move = MOVE_SKILL_SWAP; }
+    PARAMETRIZE { move = MOVE_ENTRAINMENT; }
+
+    GIVEN {
+        ASSUME(gBattleMoves[MOVE_ROLE_PLAY].effect == EFFECT_ROLE_PLAY);
+        ASSUME(gBattleMoves[MOVE_SKILL_SWAP].effect == EFFECT_SKILL_SWAP);
+        ASSUME(gBattleMoves[MOVE_ENTRAINMENT].effect == EFFECT_ENTRAINMENT);
+        PLAYER(SPECIES_PALAFIN_ZERO) { Ability(ABILITY_ZERO_TO_HERO); }
+        OPPONENT(SPECIES_WOBBUFFET);
+    } WHEN {
+        TURN { MOVE(player, move); }
+    } SCENE {
+        NOT ANIMATION(ANIM_TYPE_MOVE, move, player);
+        MESSAGE("But it failed!");
+    }
+}
+
+// Write Trace test and move this one to that file (including every other ability that can't be copied)
+SINGLE_BATTLE_TEST("Zero to Hero cannot be copied by Trace")
+{
+    GIVEN {
+        PLAYER(SPECIES_PALAFIN_ZERO) { Ability(ABILITY_ZERO_TO_HERO); }
+        OPPONENT(SPECIES_RALTS) { Ability(ABILITY_TRACE); }
+    } WHEN {
+        TURN {}
+    } SCENE {
+        NONE_OF {
+            ABILITY_POPUP(opponent, ABILITY_TRACE);
+            MESSAGE("Foe Ralts Traced Palafin's Zero to Hero!");
+        }
+    }
+}