diff --git a/cpp/src/arrow/engine/substrait/extension_set.cc b/cpp/src/arrow/engine/substrait/extension_set.cc
index 50e9bd16335eb..70d9ef1acd0f8 100644
--- a/cpp/src/arrow/engine/substrait/extension_set.cc
+++ b/cpp/src/arrow/engine/substrait/extension_set.cc
@@ -358,15 +358,19 @@ ExtensionIdRegistry* default_extension_id_registry() {
 Status FunctionMapping::AddArrowToSubstrait(std::string arrow_function_name, ArrowToSubstrait conversion_func){
   if (arrow_to_substrait.find(arrow_function_name) != arrow_to_substrait.end()){
     arrow_to_substrait[arrow_function_name] =  conversion_func;
+    return Status::OK();
+  } else{
+    return Status::Invalid("Arrow function already exist in the conversion map");
   }
-  return Status::OK();
 }
 
 Status FunctionMapping::AddSubstraitToArrow(std::string substrait_function_name, SubstraitToArrow conversion_func){
   if (substrait_to_arrow.find(substrait_function_name) != substrait_to_arrow.end()){
     substrait_to_arrow[substrait_function_name] =  conversion_func;
+    return Status::OK();
+  } else{
+    return Status::Invalid("Substrait function already exist in the conversion map");
   }
-  return Status::OK();
 }
 
 Result<SubstraitToArrow> FunctionMapping::GetArrowFromSubstrait(std::string name) const {