diff --git a/include/constants/pokemon.h b/include/constants/pokemon.h
index 186ef5de5996..424919cc440f 100644
--- a/include/constants/pokemon.h
+++ b/include/constants/pokemon.h
@@ -289,8 +289,8 @@
 #define EVO_LEVEL_FOG                     42     // Pokémon reaches the specified level during fog in the overworld
 #define EVO_MOVE_TWO_SEGMENT              43     // Pokémon levels up, knows specified move, has a personality value with a modulus of 0
 #define EVO_MOVE_THREE_SEGMENT            44     // Pokémon levels up, knows specified move, has a personality value with a modulus of 1-99
-#define EVO_LEVEL_FAMILY_OF_THREE         45     // Pokémon reaches the specified level with a personality value with a modulus of 0
-#define EVO_LEVEL_FAMILY_OF_FOUR          46     // Pokémon reaches the specified level with a personality value with a modulus of 1-99
+#define EVO_LEVEL_FAMILY_OF_THREE         45     // Pokémon reaches the specified level in battle with a personality value with a modulus of 0
+#define EVO_LEVEL_FAMILY_OF_FOUR          46     // Pokémon reaches the specified level in battle with a personality value with a modulus of 1-99
 #define EVO_LEVEL_MOVE_TWENTY_TIMES       47     // Pokémon levels up after having used a move for at least 20 times
 #define EVO_LEVEL_RECOIL_DAMAGE_MALE      48     // Pokémon levels up after having suffered specified amount of non-fainting recoil damage as a male
 #define EVO_LEVEL_RECOIL_DAMAGE_FEMALE    49     // Pokémon levels up after having suffered specified amount of non-fainting recoil damage as a female
@@ -302,6 +302,7 @@
 #define EVO_MODE_ITEM_CHECK        3 // If an Everstone is being held, still want to show that the stone *could* be used on that Pokémon to evolve
 #define EVO_MODE_BATTLE_SPECIAL    4
 #define EVO_MODE_OVERWORLD_SPECIAL 5
+#define EVO_MODE_BATTLE_ONLY       6 // This mode is only used in battles to support Tandemaus' unique requirement
 
 #define MON_PIC_WIDTH 64
 #define MON_PIC_HEIGHT 64
diff --git a/src/battle_main.c b/src/battle_main.c
index 4d64ed46b2f6..af073cafb6c5 100644
--- a/src/battle_main.c
+++ b/src/battle_main.c
@@ -5837,7 +5837,7 @@ static void TryEvolvePokemon(void)
             if (species == SPECIES_NONE && (gLeveledUpInBattle & gBitTable[i]))
             { 
                 gLeveledUpInBattle &= ~(gBitTable[i]);
-                species = GetEvolutionTargetSpecies(&gPlayerParty[i], EVO_MODE_NORMAL, gLeveledUpInBattle, NULL);
+                species = GetEvolutionTargetSpecies(&gPlayerParty[i], EVO_MODE_BATTLE_ONLY, gLeveledUpInBattle, NULL);
             }
 
             if (species != SPECIES_NONE)
diff --git a/src/pokemon.c b/src/pokemon.c
index 763c044c7655..e33f55472a96 100644
--- a/src/pokemon.c
+++ b/src/pokemon.c
@@ -4176,6 +4176,7 @@ u16 GetEvolutionTargetSpecies(struct Pokemon *mon, u8 mode, u16 evolutionItem, s
     switch (mode)
     {
     case EVO_MODE_NORMAL:
+    case EVO_MODE_BATTLE_ONLY:
         level = GetMonData(mon, MON_DATA_LEVEL, 0);
         friendship = GetMonData(mon, MON_DATA_FRIENDSHIP, 0);
 
@@ -4264,11 +4265,11 @@ u16 GetEvolutionTargetSpecies(struct Pokemon *mon, u8 mode, u16 evolutionItem, s
                     targetSpecies = evolutions[i].targetSpecies;
                 break;
             case EVO_LEVEL_FAMILY_OF_FOUR:
-                if (evolutions[i].param <= level && (personality % 100) != 0)
+                if (mode == EVO_MODE_BATTLE_ONLY && evolutions[i].param <= level && (personality % 100) != 0)
                     targetSpecies = evolutions[i].targetSpecies;
                 break;
             case EVO_LEVEL_FAMILY_OF_THREE:
-                if (evolutions[i].param <= level && (personality % 100) == 0)
+                if (mode == EVO_MODE_BATTLE_ONLY && evolutions[i].param <= level && (personality % 100) == 0)
                     targetSpecies = evolutions[i].targetSpecies;
                 break;
             case EVO_BEAUTY: