diff --git a/include/random.h b/include/random.h
index 24b5b7bdf2..709f28cb9e 100644
--- a/include/random.h
+++ b/include/random.h
@@ -183,6 +183,7 @@ enum RandomTag
     RNG_SPEED_TIE,
     RNG_STATIC,
     RNG_STENCH,
+    RNG_TOXIC_CHAIN,
     RNG_TRI_ATTACK,
     RNG_QUICK_DRAW,
     RNG_QUICK_CLAW,
diff --git a/src/battle_util.c b/src/battle_util.c
index 22de9da2f8..9fc6e9fe5f 100644
--- a/src/battle_util.c
+++ b/src/battle_util.c
@@ -5806,6 +5806,22 @@ u32 AbilityBattleEffects(u32 caseID, u32 battler, u32 ability, u32 special, u32
                 effect++;
             }
             break;
+        case ABILITY_TOXIC_CHAIN:
+            if (!(gMoveResultFlags & MOVE_RESULT_NO_EFFECT)
+             && IsBattlerAlive(gBattlerTarget)
+             && !gProtectStructs[gBattlerAttacker].confusionSelfDmg
+             && CanBePoisoned(gBattlerAttacker, gBattlerTarget)
+             && TARGET_TURN_DAMAGED // Need to actually hit the target
+             && RandomWeighted(RNG_TOXIC_CHAIN, 7, 3))
+            {
+                gBattleScripting.moveEffect = MOVE_EFFECT_TOXIC;
+                PREPARE_ABILITY_BUFFER(gBattleTextBuff1, gLastUsedAbility);
+                BattleScriptPushCursor();
+                gBattlescriptCurrInstr = BattleScript_AbilityStatusEffect;
+                gHitMarker |= HITMARKER_STATUS_ABILITY_EFFECT;
+                effect++;
+            }
+            break;
         case ABILITY_STENCH:
             if (!(gMoveResultFlags & MOVE_RESULT_NO_EFFECT)
              && IsBattlerAlive(gBattlerTarget)
@@ -7955,6 +7971,18 @@ u8 ItemBattleEffects(u8 caseID, u32 battler, bool32 moveTurn)
             case HOLD_EFFECT_MARANGA_BERRY:  // consume and boost sp. defense if used special move
                 effect = DamagedStatBoostBerryEffect(battler, STAT_SPDEF, DAMAGE_CATEGORY_SPECIAL);
                 break;
+            case HOLD_EFFECT_CURE_STATUS: // only Toxic Chain's interaction with Knock Off
+            case HOLD_EFFECT_CURE_PSN:
+                if (gBattleMons[battler].status1 & STATUS1_PSN_ANY && !UnnerveOn(battler, gLastUsedItem) && GetBattlerAbility(gBattlerAttacker) == ABILITY_TOXIC_CHAIN && gMovesInfo[gCurrentMove].effect == EFFECT_KNOCK_OFF)
+                {
+                    gBattleScripting.battler = battler;
+                    gBattleMons[battler].status1 &= ~(STATUS1_PSN_ANY | STATUS1_TOXIC_COUNTER);
+                    BattleScriptExecute(BattleScript_BerryCurePsnEnd2);
+                    BtlController_EmitSetMonData(battler, 0, REQUEST_STATUS_BATTLE, 0, 4, &gBattleMons[battler].status1);
+                    MarkBattlerForControllerExec(battler);
+                    effect = ITEM_STATUS_CHANGE;
+                }
+                break;
             case HOLD_EFFECT_STICKY_BARB:
                 if (TARGET_TURN_DAMAGED
                   && (!(gMoveResultFlags & MOVE_RESULT_NO_EFFECT))
diff --git a/test/battle/ability/toxic_chain.c b/test/battle/ability/toxic_chain.c
new file mode 100644
index 0000000000..d6aba06f70
--- /dev/null
+++ b/test/battle/ability/toxic_chain.c
@@ -0,0 +1,112 @@
+#include "global.h"
+#include "test/battle.h"
+
+SINGLE_BATTLE_TEST("Toxic Chain inflicts bad poison when attacking")
+{
+    PASSES_RANDOMLY(3, 10, RNG_TOXIC_CHAIN);
+    GIVEN {
+        ASSUME(gMovesInfo[MOVE_TACKLE].category != DAMAGE_CATEGORY_STATUS);
+        ASSUME(gMovesInfo[MOVE_TACKLE].power > 0);
+        PLAYER(SPECIES_OKIDOGI) { Ability(ABILITY_TOXIC_CHAIN); }
+        OPPONENT(SPECIES_WOBBUFFET);
+    } WHEN {
+        TURN { MOVE(player, MOVE_TACKLE); }
+    } SCENE {
+        ABILITY_POPUP(player, ABILITY_TOXIC_CHAIN);
+        ANIMATION(ANIM_TYPE_STATUS, B_ANIM_STATUS_PSN, opponent);
+        MESSAGE("Foe Wobbuffet is badly poisoned!");
+        STATUS_ICON(opponent, badPoison: TRUE);
+    } THEN {
+        EXPECT(opponent->status1 & STATUS1_TOXIC_POISON);
+    }
+}
+
+SINGLE_BATTLE_TEST("Toxic Chain inflicts bad poison on any hit of a multi-hit move")
+{
+    GIVEN {
+        ASSUME(gMovesInfo[MOVE_DOUBLE_SLAP].category != DAMAGE_CATEGORY_STATUS);
+        ASSUME(gMovesInfo[MOVE_DOUBLE_SLAP].effect == EFFECT_MULTI_HIT);
+        ASSUME(gMovesInfo[MOVE_DOUBLE_SLAP].power > 0);
+        ASSUME(gItemsInfo[ITEM_PECHA_BERRY].holdEffect == HOLD_EFFECT_CURE_PSN);
+        PLAYER(SPECIES_OKIDOGI) { Ability(ABILITY_TOXIC_CHAIN); }
+        OPPONENT(SPECIES_WOBBUFFET) { Item(ITEM_PECHA_BERRY); }
+    } WHEN {
+        TURN { MOVE(player, MOVE_DOUBLE_SLAP); }
+    } SCENE {
+        ABILITY_POPUP(player, ABILITY_TOXIC_CHAIN);
+        ANIMATION(ANIM_TYPE_STATUS, B_ANIM_STATUS_PSN, opponent);
+        MESSAGE("Foe Wobbuffet is badly poisoned!");
+        STATUS_ICON(opponent, badPoison: TRUE);
+        ANIMATION(ANIM_TYPE_GENERAL, B_ANIM_HELD_ITEM_EFFECT, opponent);
+        STATUS_ICON(opponent, badPoison: FALSE);
+        ABILITY_POPUP(player, ABILITY_TOXIC_CHAIN);
+        ANIMATION(ANIM_TYPE_STATUS, B_ANIM_STATUS_PSN, opponent);
+        MESSAGE("Foe Wobbuffet is badly poisoned!");
+        STATUS_ICON(opponent, badPoison: TRUE);
+    } THEN {
+        EXPECT(opponent->status1 & STATUS1_TOXIC_POISON);
+    }
+}
+
+DOUBLE_BATTLE_TEST("Toxic Chain can inflict bad poison on both foes")
+{
+    GIVEN {
+        ASSUME(gMovesInfo[MOVE_RAZOR_LEAF].category != DAMAGE_CATEGORY_STATUS);
+        ASSUME(gMovesInfo[MOVE_RAZOR_LEAF].target == MOVE_TARGET_BOTH);
+        ASSUME(gMovesInfo[MOVE_RAZOR_LEAF].power > 0);
+        PLAYER(SPECIES_OKIDOGI) { Ability(ABILITY_TOXIC_CHAIN); }
+        PLAYER(SPECIES_WOBBUFFET);
+        OPPONENT(SPECIES_WOBBUFFET);
+        OPPONENT(SPECIES_WYNAUT);
+    } WHEN {
+        TURN { MOVE(playerLeft, MOVE_RAZOR_LEAF, WITH_RNG(RNG_TOXIC_CHAIN, TRUE)); }
+    } SCENE {
+        HP_BAR(opponentLeft);
+        ABILITY_POPUP(playerLeft, ABILITY_TOXIC_CHAIN);
+        ANIMATION(ANIM_TYPE_STATUS, B_ANIM_STATUS_PSN, opponentLeft);
+        MESSAGE("Foe Wobbuffet is badly poisoned!");
+        STATUS_ICON(opponentLeft, badPoison: TRUE);
+        HP_BAR(opponentRight);
+        ABILITY_POPUP(playerLeft, ABILITY_TOXIC_CHAIN);
+        ANIMATION(ANIM_TYPE_STATUS, B_ANIM_STATUS_PSN, opponentRight);
+        MESSAGE("Foe Wynaut is badly poisoned!");
+        STATUS_ICON(opponentRight, badPoison: TRUE);
+    } THEN {
+        EXPECT(opponentLeft->status1 & STATUS1_TOXIC_POISON);
+        EXPECT(opponentRight->status1 & STATUS1_TOXIC_POISON);
+    }
+}
+
+SINGLE_BATTLE_TEST("Toxic Chain makes Lum/Pecha Berry trigger before being knocked off")
+{
+    u16 item = 0;
+
+    PARAMETRIZE { item = ITEM_PECHA_BERRY; }
+    PARAMETRIZE { item = ITEM_LUM_BERRY; }
+
+    GIVEN {
+        ASSUME(gMovesInfo[MOVE_KNOCK_OFF].category != DAMAGE_CATEGORY_STATUS);
+        ASSUME(gMovesInfo[MOVE_KNOCK_OFF].effect == EFFECT_KNOCK_OFF);
+        ASSUME(gMovesInfo[MOVE_KNOCK_OFF].power > 0);
+        ASSUME(gItemsInfo[ITEM_PECHA_BERRY].holdEffect == HOLD_EFFECT_CURE_PSN);
+        ASSUME(gItemsInfo[ITEM_LUM_BERRY].holdEffect == HOLD_EFFECT_CURE_STATUS);
+        PLAYER(SPECIES_OKIDOGI) { Ability(ABILITY_TOXIC_CHAIN); }
+        OPPONENT(SPECIES_WOBBUFFET) { Item(item); }
+    } WHEN {
+        TURN { MOVE(player, MOVE_KNOCK_OFF, WITH_RNG(RNG_TOXIC_CHAIN, TRUE)); }
+    } SCENE {
+        ABILITY_POPUP(player, ABILITY_TOXIC_CHAIN);
+        ANIMATION(ANIM_TYPE_STATUS, B_ANIM_STATUS_PSN, opponent);
+        MESSAGE("Foe Wobbuffet is badly poisoned!");
+        STATUS_ICON(opponent, badPoison: TRUE);
+        ANIMATION(ANIM_TYPE_GENERAL, B_ANIM_HELD_ITEM_EFFECT, opponent);
+        STATUS_ICON(opponent, badPoison: FALSE);
+        NONE_OF {
+            ANIMATION(ANIM_TYPE_GENERAL, B_ANIM_ITEM_KNOCKOFF);
+            MESSAGE("Okidogi knocked off Foe Wobbuffet's Pecha Berry!");
+            MESSAGE("Okidogi knocked off Foe Wobbuffet's Lum Berry!");
+        }
+    } THEN {
+        EXPECT(opponent->status1 == 0);
+    }
+}