diff --git a/server/src-lib/Hasura/RQL/DDL/Schema/Diff.hs b/server/src-lib/Hasura/RQL/DDL/Schema/Diff.hs
index d5d4d794ffc6c..560db3558bcfb 100644
--- a/server/src-lib/Hasura/RQL/DDL/Schema/Diff.hs
+++ b/server/src-lib/Hasura/RQL/DDL/Schema/Diff.hs
@@ -17,10 +17,12 @@ module Hasura.RQL.DDL.Schema.Diff
   , fetchFunctionMeta
   , FunctionDiff(..)
   , getFuncDiff
+  , getOverloadedFuncs
   ) where
 
 import           Hasura.Prelude
 import           Hasura.RQL.Types
+import           Hasura.Server.Utils (duplicates)
 import           Hasura.SQL.Types
 
 import qualified Database.PG.Query   as Q
@@ -257,6 +259,7 @@ fetchFunctionMeta = do
       )
     WHERE
       f.function_schema <> 'hdb_catalog'
+    GROUP BY p.oid, f.function_schema, f.function_name, f.function_type
     |] () False
 
 data FunctionDiff
@@ -275,3 +278,11 @@ getFuncDiff oldMeta newMeta =
       let isTypeAltered = fmType oldfm /= fmType newfm
           alteredFunc = (funcFromMeta oldfm, fmType newfm)
       in bool Nothing (Just alteredFunc) isTypeAltered
+
+getOverloadedFuncs
+  :: [QualifiedFunction] -> [FunctionMeta] -> [QualifiedFunction]
+getOverloadedFuncs trackedFuncs newFuncMeta =
+  duplicates $ map funcFromMeta trackedMeta
+  where
+    trackedMeta = flip filter newFuncMeta $ \fm ->
+      funcFromMeta fm `elem` trackedFuncs
diff --git a/server/src-lib/Hasura/RQL/DDL/Schema/Table.hs b/server/src-lib/Hasura/RQL/DDL/Schema/Table.hs
index 85b66c5adc46f..8535d0188a47a 100644
--- a/server/src-lib/Hasura/RQL/DDL/Schema/Table.hs
+++ b/server/src-lib/Hasura/RQL/DDL/Schema/Table.hs
@@ -442,6 +442,12 @@ execWithMDCheck (RunSQL t cascade _) = do
       existingFuncs = M.keys $ scFunctions sc
       oldFuncMeta = flip filter oldFuncMetaU $ \fm -> funcFromMeta fm `elem` existingFuncs
       FunctionDiff droppedFuncs alteredFuncs = getFuncDiff oldFuncMeta newFuncMeta
+      overloadedFuncs = getOverloadedFuncs existingFuncs newFuncMeta
+
+  -- Do not allow overloading functions
+  unless (null overloadedFuncs) $
+    throw400 NotSupported $ "the following tracked function(s) cannot be overloaded: "
+    <> reportFuncs overloadedFuncs
 
   indirectDeps <- getSchemaChangeDeps schemaDiff
 
@@ -490,12 +496,14 @@ execWithMDCheck (RunSQL t cascade _) = do
   refreshGCtxMapInSchema
 
   return res
+  where
+    reportFuncs = T.intercalate ", " . map dquoteTxt
 
 isAltrDropReplace :: QErrM m => T.Text -> m Bool
 isAltrDropReplace = either throwErr return . matchRegex regex False
   where
     throwErr s = throw500 $ "compiling regex failed: " <> T.pack s
-    regex = "alter|drop|replace"
+    regex = "alter|drop|replace|create function"
 
 runRunSQL
   :: (QErrM m, UserInfoM m, CacheRWM m, MonadTx m, MonadIO m, HasHttpManager m)
diff --git a/server/src-lib/Hasura/SQL/Types.hs b/server/src-lib/Hasura/SQL/Types.hs
index e171cb5afdf47..0d1fc30a44ec5 100644
--- a/server/src-lib/Hasura/SQL/Types.hs
+++ b/server/src-lib/Hasura/SQL/Types.hs
@@ -143,7 +143,7 @@ instance ToSQL ConstraintName where
 
 newtype FunctionName
   = FunctionName { getFunctionTxt :: T.Text }
-  deriving (Show, Eq, FromJSON, ToJSON, Q.ToPrepArg, Q.FromCol, Hashable, Lift)
+  deriving (Show, Eq, Ord, FromJSON, ToJSON, Q.ToPrepArg, Q.FromCol, Hashable, Lift)
 
 instance IsIden FunctionName where
   toIden (FunctionName t) = Iden t
@@ -159,7 +159,7 @@ instance ToTxt FunctionName where
 
 newtype SchemaName
   = SchemaName { getSchemaTxt :: T.Text }
-  deriving (Show, Eq, FromJSON, ToJSON, Hashable, Q.ToPrepArg, Q.FromCol, Lift)
+  deriving (Show, Eq, Ord, FromJSON, ToJSON, Hashable, Q.ToPrepArg, Q.FromCol, Lift)
 
 publicSchema :: SchemaName
 publicSchema = SchemaName "public"
@@ -174,7 +174,7 @@ data QualifiedObject a
   = QualifiedObject
   { qSchema :: !SchemaName
   , qName   :: !a
-  } deriving (Show, Eq, Generic, Lift)
+  } deriving (Show, Eq, Ord, Generic, Lift)
 
 instance (FromJSON a) => FromJSON (QualifiedObject a) where
   parseJSON v@(String _) =
diff --git a/server/tests-py/queries/graphql_query/functions/overloading_function_error.yaml b/server/tests-py/queries/graphql_query/functions/overloading_function_error.yaml
new file mode 100644
index 0000000000000..bacb39c67dc15
--- /dev/null
+++ b/server/tests-py/queries/graphql_query/functions/overloading_function_error.yaml
@@ -0,0 +1,20 @@
+description: Create a new SQL function with same name (error)
+url: /v1/query
+status: 400
+response:
+  path: "$.args"
+  error: 'the following tracked function(s) cannot be overloaded: search_posts'
+  code: not-supported
+query:
+  type: run_sql
+  args:
+    sql: |
+      create function search_posts(search text, id integer)
+      returns setof post as $$
+          select *
+          from post
+          where
+          title ilike ('%' || search || '%') or
+          content ilike ('%' || search || '%') or
+          id = id
+      $$ language sql stable;
diff --git a/server/tests-py/test_graphql_queries.py b/server/tests-py/test_graphql_queries.py
index 5b1188c4c7142..768300cd50d58 100644
--- a/server/tests-py/test_graphql_queries.py
+++ b/server/tests-py/test_graphql_queries.py
@@ -342,6 +342,9 @@ def test_search_posts_aggregate(self, hge_ctx):
     def test_alter_function_error(self, hge_ctx):
         check_query_f(hge_ctx, self.dir() + '/alter_function_error.yaml')
 
+    def test_overloading_function_error(self, hge_ctx):
+        check_query_f(hge_ctx, self.dir() + '/overloading_function_error.yaml')
+
     @classmethod
     def dir(cls):
         return 'queries/graphql_query/functions'