C2664: Cannot Convert Argument N from ‘type1’ to ‘type2’ in UE5 – What It Means & How to Fix It

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🧠 Why You’re Seeing This Error

The C2664 error means you’re calling a function, constructor, or method in UE5 and passing it the wrong type of argument.

The 'N' part tells you which argument (1st, 2nd, etc.) is the problem, and the compiler is saying:

I was expecting a value of type type2, but you gave me type1, and I don’t know how to convert that.

This is one of the most common and frustrating UE5 errors because UE5 has strict and custom types (FVector, FString, AActor*, etc.) that don’t always convert like standard C++ types.

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💥 Example Error Message

error C2664: 'void AActor::SetActorLocation(const FVector&)': cannot convert argument 1 from 'float' to 'const FVector &'

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🛠️ Example Code

float X = 100.f;
Actor->SetActorLocation(X); // ❌ C2664: expected FVector, got float

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✅ How to Fix C2664 in UE5 – Step-by-Step

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✔️ 1. Pass the Correct Type

Read the error: if the function wants a const FVector&, you have to give it a FVector.

Fix:

FVector Location(X, 0.f, 0.f);
Actor->SetActorLocation(Location); // ✅ Now types match

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✔️ 2. Convert FString Properly

A very common mistake: passing a string literal ("Hello") into something expecting FString.

Wrong:

FString MyName = "Player"; // ❌ Can't convert from 'const char*'

Fix:

FString MyName = FString(TEXT("Player")); // ✅ Correct in UE5

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✔️ 3. Casting Between UObject Types

When passing class pointers (like to AEnemy*), use Cast<> if the types aren’t exact.

Wrong:

TakeDamage(SomeActor); // ❌ Maybe expecting AEnemy*, not AActor*

Fix:

AEnemy* Enemy = Cast(SomeActor);
TakeDamage(Enemy); // ✅

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✔️ 4. Make Sure You’re Not Missing a & or *

UE5 functions often expect references or pointers. Double-check the function signature.

Wrong:

FVector Location;
SomeFunction(Location); // ❌ Expects a pointer maybe

Fix:

SomeFunction(&Location); // ✅ If function wants a pointer

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✅ Summary: How to Fix C2664 in UE5

Cause	Fix Example
Passing wrong type	Match exactly what the function expects
String literal to FString	Use FString(TEXT("..."))
Wrong object pointer type	Use Cast<>() to safely convert UObject pointers
Missing * or & in argument	Check if function needs a pointer or reference