diff --git a/src/utilities/__tests__/coerceInputValue-test.ts b/src/utilities/__tests__/coerceInputValue-test.ts
index 5f46b066d1..f8910bd5ba 100644
--- a/src/utilities/__tests__/coerceInputValue-test.ts
+++ b/src/utilities/__tests__/coerceInputValue-test.ts
@@ -598,6 +598,7 @@ describe('coerceInputLiteral', () => {
     test('{ a: null }', testOneOfInputObj, undefined);
     test('{ a: 1 }', testOneOfInputObj, undefined);
     test('{ a: "abc", b: "def" }', testOneOfInputObj, undefined);
+    test('{ a: "abc", c: "def" }', testOneOfInputObj, undefined);
     test('{}', testOneOfInputObj, undefined);
     test('{ c: "abc" }', testOneOfInputObj, undefined);
   });
diff --git a/src/utilities/__tests__/validateInputValue-test.ts b/src/utilities/__tests__/validateInputValue-test.ts
index 31cdd57490..cc8ccb16c0 100644
--- a/src/utilities/__tests__/validateInputValue-test.ts
+++ b/src/utilities/__tests__/validateInputValue-test.ts
@@ -443,34 +443,31 @@ describe('validateInputValue', () => {
     });
 
     it('returns error for an unknown field', () => {
-      // TODO: not technically a OneOf error, as the OneOf validation assumes known fields
       test({ foo: 123, unknownField: 123 }, TestInputObject, [
         {
           error:
             'Expected value of type "TestInputObject" not to include unknown field "unknownField", found: { foo: 123, unknownField: 123 }.',
           path: [],
         },
-        {
-          error:
-            'Within OneOf Input Object type "TestInputObject", exactly one field must be specified, and the value for that field must be non-null.',
-          path: [],
-        },
       ]);
     });
 
     it('returns error for a misspelled field', () => {
-      // TODO: technically also a OneOf error, as the OneOf validation assumes known fields, so there are no errors here
       test({ bart: 123 }, TestInputObject, [
         {
           error:
             'Expected value of type "TestInputObject" not to include unknown field "bart". Did you mean "bar"? Found: { bart: 123 }.',
           path: [],
         },
+        {
+          error:
+            'Within OneOf Input Object type "TestInputObject", exactly one field must be specified, and the value for that field must be non-null.',
+          path: [],
+        },
       ]);
     });
 
     it('returns error for a misspelled field (no suggestions)', () => {
-      // TODO: technically also a OneOf error, as the OneOf validation assumes known fields, so there are no errors here
       test(
         { bart: 123 },
         TestInputObject,
@@ -480,6 +477,11 @@ describe('validateInputValue', () => {
               'Expected value of type "TestInputObject" not to include unknown field "bart", found: { bart: 123 }.',
             path: [],
           },
+          {
+            error:
+              'Within OneOf Input Object type "TestInputObject", exactly one field must be specified, and the value for that field must be non-null.',
+            path: [],
+          },
         ],
         true,
       );
@@ -1016,34 +1018,22 @@ describe('validateInputLiteral', () => {
     });
 
     it('returns error for an unknown field', () => {
-      // TODO: not technically a OneOf error, as the OneOf validation assumes known fields
       test('{ foo: 123, unknownField: 123 }', TestInputObject, [
         {
           error:
             'Expected value of type "TestInputObject" not to include unknown field "unknownField", found: { foo: 123, unknownField: 123 }.',
           path: [],
         },
-        {
-          error:
-            'Within OneOf Input Object type "TestInputObject", exactly one field must be specified, and the value for that field must be non-null.',
-          path: [],
-        },
       ]);
     });
 
     it('returns error for a misspelled field', () => {
-      // TODO: not technically a OneOf error, as the OneOf validation assumes known fields
       test('{ foo: 123, bart: 123 }', TestInputObject, [
         {
           error:
             'Expected value of type "TestInputObject" not to include unknown field "bart". Did you mean "bar"? Found: { foo: 123, bart: 123 }.',
           path: [],
         },
-        {
-          error:
-            'Within OneOf Input Object type "TestInputObject", exactly one field must be specified, and the value for that field must be non-null.',
-          path: [],
-        },
       ]);
     });
 
diff --git a/src/utilities/validateInputValue.ts b/src/utilities/validateInputValue.ts
index 865a7b81a1..0beac679d4 100644
--- a/src/utilities/validateInputValue.ts
+++ b/src/utilities/validateInputValue.ts
@@ -150,7 +150,6 @@ function validateInputValueImpl(
       if (inputValue[fieldName] === undefined) {
         continue;
       }
-      fields.push(fieldName);
       if (!Object.hasOwn(fieldDefs, fieldName)) {
         const suggestion = hideSuggestions
           ? ''
@@ -162,7 +161,9 @@ function validateInputValueImpl(
           }: ${inspect(inputValue)}.`,
           path,
         );
+        continue;
       }
+      fields.push(fieldName);
     }
 
     if (type.isOneOf) {
@@ -414,6 +415,7 @@ function validateInputLiteralImpl(
     }
 
     const fields = valueNode.fields;
+    const knownFields: Array<(typeof fields)[number]> = [];
     // Ensure every provided field is defined.
     for (const fieldNode of fields) {
       const fieldName = fieldNode.name.value;
@@ -429,11 +431,13 @@ function validateInputLiteralImpl(
           fieldNode,
           path,
         );
+      } else {
+        knownFields.push(fieldNode);
       }
     }
 
     if (type.isOneOf) {
-      const isNotExactlyOneField = fields.length !== 1;
+      const isNotExactlyOneField = knownFields.length !== 1;
       if (isNotExactlyOneField) {
         reportInvalidLiteral(
           context.onError,
@@ -444,9 +448,9 @@ function validateInputLiteralImpl(
         return;
       }
 
-      const fieldValueNode = fields[0].value;
+      const fieldValueNode = knownFields[0].value;
       if (fieldValueNode.kind === Kind.NULL) {
-        const fieldName = fields[0].name.value;
+        const fieldName = knownFields[0].name.value;
         reportInvalidLiteral(
           context.onError,
           getOneOfInputObjectErrorMessage(type),
diff --git a/src/validation/__tests__/ValuesOfCorrectTypeRule-test.ts b/src/validation/__tests__/ValuesOfCorrectTypeRule-test.ts
index 38dbcdcfd5..3f106dfc5f 100644
--- a/src/validation/__tests__/ValuesOfCorrectTypeRule-test.ts
+++ b/src/validation/__tests__/ValuesOfCorrectTypeRule-test.ts
@@ -1168,6 +1168,25 @@ describe('Validate: Values of correct type', () => {
         },
       ]);
     });
+
+    it('Unknown field does not add a oneOf error', () => {
+      expectErrors(`
+          {
+            complicatedArgs {
+              oneOfArgField(oneOfArg: {
+                stringField: "abc",
+                invalidField: 123
+              })
+            }
+          }
+        `).toDeepEqual([
+        {
+          message:
+            'Expected value of type "OneOfInput" not to include unknown field "invalidField". Did you mean "intField"? Found: { stringField: "abc", invalidField: 123 }.',
+          locations: [{ line: 6, column: 17 }],
+        },
+      ]);
+    });
   });
 
   describe('Directive arguments', () => {