diff --git a/src/type/__tests__/scalars-test.ts b/src/type/__tests__/scalars-test.ts
index 4d563aee10..73c1b345c8 100644
--- a/src/type/__tests__/scalars-test.ts
+++ b/src/type/__tests__/scalars-test.ts
@@ -161,17 +161,14 @@ describe('Type System: Specified scalar types', () => {
       expect(() => serialize(-1e100)).to.throw(
         'Int cannot represent non 32-bit signed integer value: -1e+100',
       );
-      expect(() => serialize('one')).to.throw(
-        'Int cannot represent non-integer value: "one"',
-      );
 
       // Doesn't represent number
       expect(() => serialize('')).to.throw(
         'Int cannot represent non-integer value: ""',
       );
-      expect(() => serialize(NaN)).to.throw(
-        'Int cannot represent non-integer value: NaN',
-      );
+
+      expect(serialize(NaN)).to.equal(null);
+
       expect(() => serialize(Infinity)).to.throw(
         'Int cannot represent non-integer value: Infinity',
       );
@@ -293,18 +290,11 @@ describe('Type System: Specified scalar types', () => {
       };
       expect(serialize(customValueOfObj)).to.equal(5.5);
 
-      expect(() => serialize(NaN)).to.throw(
-        'Float cannot represent non numeric value: NaN',
-      );
+      expect(serialize(NaN)).to.equal(null);
+
       expect(() => serialize(Infinity)).to.throw(
         'Float cannot represent non numeric value: Infinity',
       );
-      expect(() => serialize('one')).to.throw(
-        'Float cannot represent non numeric value: "one"',
-      );
-      expect(() => serialize('')).to.throw(
-        'Float cannot represent non numeric value: ""',
-      );
       expect(() => serialize([5])).to.throw(
         'Float cannot represent non numeric value: [5]',
       );
diff --git a/src/type/scalars.ts b/src/type/scalars.ts
index 4990347887..fa5c55ab75 100644
--- a/src/type/scalars.ts
+++ b/src/type/scalars.ts
@@ -21,7 +21,7 @@ export const GRAPHQL_MAX_INT = 2147483647;
  * */
 export const GRAPHQL_MIN_INT = -2147483648;
 
-export const GraphQLInt = new GraphQLScalarType<number>({
+export const GraphQLInt = new GraphQLScalarType<number | null>({
   name: 'Int',
   description:
     'The `Int` scalar type represents non-fractional signed whole numeric values. Int can represent values between -(2^31) and 2^31 - 1.',
@@ -38,6 +38,10 @@ export const GraphQLInt = new GraphQLScalarType<number>({
       num = Number(coercedValue);
     }
 
+    if (typeof num === 'number' && Number.isNaN(num)) {
+      return null;
+    }
+
     if (typeof num !== 'number' || !Number.isInteger(num)) {
       throw new GraphQLError(
         `Int cannot represent non-integer value: ${inspect(coercedValue)}`,
@@ -84,7 +88,7 @@ export const GraphQLInt = new GraphQLScalarType<number>({
   },
 });
 
-export const GraphQLFloat = new GraphQLScalarType<number>({
+export const GraphQLFloat = new GraphQLScalarType<number | null>({
   name: 'Float',
   description:
     'The `Float` scalar type represents signed double-precision fractional values as specified by [IEEE 754](https://en.wikipedia.org/wiki/IEEE_floating_point).',
@@ -101,6 +105,10 @@ export const GraphQLFloat = new GraphQLScalarType<number>({
       num = Number(coercedValue);
     }
 
+    if (typeof num === 'number' && Number.isNaN(num)) {
+      return null;
+    }
+
     if (typeof num !== 'number' || !Number.isFinite(num)) {
       throw new GraphQLError(
         `Float cannot represent non numeric value: ${inspect(coercedValue)}`,
diff --git a/src/utilities/__tests__/astFromValue-test.ts b/src/utilities/__tests__/astFromValue-test.ts
index b8f2361bd7..71a5ba09c7 100644
--- a/src/utilities/__tests__/astFromValue-test.ts
+++ b/src/utilities/__tests__/astFromValue-test.ts
@@ -79,10 +79,6 @@ describe('astFromValue', () => {
     expect(() => astFromValue(1e40, GraphQLInt)).to.throw(
       'Int cannot represent non 32-bit signed integer value: 1e+40',
     );
-
-    expect(() => astFromValue(NaN, GraphQLInt)).to.throw(
-      'Int cannot represent non-integer value: NaN',
-    );
   });
 
   it('converts Float values to Int/Float ASTs', () => {