diff --git a/src/libraries/System.Text.Json/src/System/ReflectionExtensions.cs b/src/libraries/System.Text.Json/src/System/ReflectionExtensions.cs
index 006c9c4e0e3ab..6cc6dbbf91e70 100644
--- a/src/libraries/System.Text.Json/src/System/ReflectionExtensions.cs
+++ b/src/libraries/System.Text.Json/src/System/ReflectionExtensions.cs
@@ -43,5 +43,24 @@ public static bool IsAssignableFromInternal(this Type type, Type from)
 
         private static bool HasJsonConstructorAttribute(ConstructorInfo constructorInfo)
             => constructorInfo.GetCustomAttribute<JsonConstructorAttribute>() != null;
+
+        public static TAttribute? GetUniqueCustomAttribute<TAttribute>(this MemberInfo memberInfo, bool inherit)
+            where TAttribute : Attribute
+        {
+            object[] attributes = memberInfo.GetCustomAttributes(typeof(TAttribute), inherit);
+
+            if (attributes.Length == 0)
+            {
+                return null;
+            }
+
+            if (attributes.Length == 1)
+            {
+                return (TAttribute)attributes[0];
+            }
+
+            ThrowHelper.ThrowInvalidOperationException_SerializationDuplicateAttribute(typeof(TAttribute), memberInfo);
+            return null;
+        }
     }
 }
diff --git a/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptions.Converters.cs b/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptions.Converters.cs
index 6ab528b639428..bdf26c36dfb9c 100644
--- a/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptions.Converters.cs
+++ b/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptions.Converters.cs
@@ -32,9 +32,7 @@ public sealed partial class JsonSerializerOptions
             Debug.Assert(memberInfo.DeclaringType != null, "Properties and fields always have a declaring type.");
             JsonConverter? converter = null;
 
-            JsonConverterAttribute? converterAttribute = (JsonConverterAttribute?)
-                GetAttributeThatCanHaveMultiple(memberInfo.DeclaringType, typeof(JsonConverterAttribute), memberInfo);
-
+            JsonConverterAttribute? converterAttribute = memberInfo.GetUniqueCustomAttribute<JsonConverterAttribute>(inherit: false);
             if (converterAttribute != null)
             {
                 converter = GetConverterFromAttribute(converterAttribute, typeToConvert, memberInfo);
@@ -176,9 +174,7 @@ private JsonConverter GetConverterFromOptionsOrReflectionConverter(Type typeToCo
             // Priority 2: Attempt to get converter from [JsonConverter] on the type being converted.
             if (converter == null)
             {
-                JsonConverterAttribute? converterAttribute = (JsonConverterAttribute?)
-                    GetAttributeThatCanHaveMultiple(typeToConvert, typeof(JsonConverterAttribute));
-
+                JsonConverterAttribute? converterAttribute = typeToConvert.GetUniqueCustomAttribute<JsonConverterAttribute>(inherit: false);
                 if (converterAttribute != null)
                 {
                     converter = GetConverterFromAttribute(converterAttribute, typeToConvert: typeToConvert, memberInfo: null);
@@ -257,33 +253,5 @@ private JsonConverter GetConverterFromAttribute(JsonConverterAttribute converter
 
             return converter;
         }
-
-        private static Attribute? GetAttributeThatCanHaveMultiple(Type classType, Type attributeType, MemberInfo memberInfo)
-        {
-            object[] attributes = memberInfo.GetCustomAttributes(attributeType, inherit: false);
-            return GetAttributeThatCanHaveMultiple(attributeType, classType, memberInfo, attributes);
-        }
-
-        internal static Attribute? GetAttributeThatCanHaveMultiple(Type classType, Type attributeType)
-        {
-            object[] attributes = classType.GetCustomAttributes(attributeType, inherit: false);
-            return GetAttributeThatCanHaveMultiple(attributeType, classType, null, attributes);
-        }
-
-        private static Attribute? GetAttributeThatCanHaveMultiple(Type attributeType, Type classType, MemberInfo? memberInfo, object[] attributes)
-        {
-            if (attributes.Length == 0)
-            {
-                return null;
-            }
-
-            if (attributes.Length == 1)
-            {
-                return (Attribute)attributes[0];
-            }
-
-            ThrowHelper.ThrowInvalidOperationException_SerializationDuplicateAttribute(attributeType, classType, memberInfo);
-            return default;
-        }
     }
 }
diff --git a/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/ReflectionJsonTypeInfoOfT.cs b/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/ReflectionJsonTypeInfoOfT.cs
index 3112df742dd96..22f322478ec60 100644
--- a/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/ReflectionJsonTypeInfoOfT.cs
+++ b/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/ReflectionJsonTypeInfoOfT.cs
@@ -212,9 +212,7 @@ private void CacheMember(
 
         private static JsonNumberHandling? GetNumberHandlingForType(Type type)
         {
-            var numberHandlingAttribute =
-                (JsonNumberHandlingAttribute?)JsonSerializerOptions.GetAttributeThatCanHaveMultiple(type, typeof(JsonNumberHandlingAttribute));
-
+            JsonNumberHandlingAttribute? numberHandlingAttribute = type.GetUniqueCustomAttribute<JsonNumberHandlingAttribute>(inherit: false);
             return numberHandlingAttribute?.Handling;
         }
 
diff --git a/src/libraries/System.Text.Json/src/System/Text/Json/ThrowHelper.Serialization.cs b/src/libraries/System.Text.Json/src/System/Text/Json/ThrowHelper.Serialization.cs
index 88f72117763ba..b65ab991d8897 100644
--- a/src/libraries/System.Text.Json/src/System/Text/Json/ThrowHelper.Serialization.cs
+++ b/src/libraries/System.Text.Json/src/System/Text/Json/ThrowHelper.Serialization.cs
@@ -398,14 +398,9 @@ public static void AddJsonExceptionInformation(ref WriteStack state, JsonExcepti
         }
 
         [DoesNotReturn]
-        public static void ThrowInvalidOperationException_SerializationDuplicateAttribute(Type attribute, Type classType, MemberInfo? memberInfo)
+        public static void ThrowInvalidOperationException_SerializationDuplicateAttribute(Type attribute, MemberInfo memberInfo)
         {
-            string location = classType.ToString();
-            if (memberInfo != null)
-            {
-                location += $".{memberInfo.Name}";
-            }
-
+            string location = memberInfo is Type type ? type.ToString() : $"{memberInfo.DeclaringType}.{memberInfo.Name}";
             throw new InvalidOperationException(SR.Format(SR.SerializationDuplicateAttribute, attribute, location));
         }