diff --git a/src/Common/ErrorCodes.cpp b/src/Common/ErrorCodes.cpp
index ad0463db889..b6523d772f2 100644
--- a/src/Common/ErrorCodes.cpp
+++ b/src/Common/ErrorCodes.cpp
@@ -549,6 +549,7 @@
     M(579, INCORRECT_PART_TYPE) \
     M(580, CANNOT_SET_ROUNDING_MODE) \
     M(581, TOO_LARGE_DISTRIBUTED_DEPTH) \
+    M(582, FUNCTION_ALREADY_EXISTS) \
     \
     M(998, POSTGRESQL_CONNECTION_FAILURE) \
     M(999, KEEPER_EXCEPTION) \
diff --git a/src/Functions/FunctionFactory.cpp b/src/Functions/FunctionFactory.cpp
index 69a34d4d030..8f71db3df7f 100644
--- a/src/Functions/FunctionFactory.cpp
+++ b/src/Functions/FunctionFactory.cpp
@@ -22,6 +22,7 @@ namespace ErrorCodes
 {
     extern const int UNKNOWN_FUNCTION;
     extern const int LOGICAL_ERROR;
+    extern const int FUNCTION_ALREADY_EXISTS;
 }
 
 const String & getFunctionCanonicalNameIfAny(const String & name)
@@ -140,6 +141,9 @@ void FunctionFactory::registerUserDefinedFunction(
         const ASTCreateFunctionQuery & create_function_query,
         CaseSensitiveness case_sensitiveness)
 {
+    if (hasNameOrAlias(create_function_query.function_name))
+        throw Exception("The function '" + create_function_query.function_name + "' already exists", ErrorCodes::FUNCTION_ALREADY_EXISTS);
+
     registerFunction(create_function_query.function_name, [create_function_query](ContextPtr context)
     {
         auto function = UserDefinedFunction::create(context);