diff --git a/src/scalars/iso-date/DateTime.ts b/src/scalars/iso-date/DateTime.ts
index 2779df420..98fdddbea 100644
--- a/src/scalars/iso-date/DateTime.ts
+++ b/src/scalars/iso-date/DateTime.ts
@@ -33,7 +33,16 @@ export const GraphQLDateTimeConfig: GraphQLScalarTypeConfig<Date, Date> = /*#__P
       throw createGraphQLError(`DateTime cannot represent an invalid date-time-string ${value}.`);
     } else if (typeof value === 'number') {
       try {
-        return new Date(value);
+        // This should support 13 and 12-digit timestamps
+        if (
+          (value <= 9999999999999 && value.toString().length === 13) ||
+          (value <= 999999999999 && value.toString().length === 12)
+        ) {
+          return new Date(value);
+        } else {
+          // Convert to milliseconds
+          return new Date(value * 1000);
+        }
       } catch (e) {
         throw createGraphQLError('DateTime cannot represent an invalid Unix timestamp ' + value);
       }
diff --git a/tests/iso-date/DateTime.integration.test.ts b/tests/iso-date/DateTime.integration.test.ts
index 6e73208d0..a365c0058 100644
--- a/tests/iso-date/DateTime.integration.test.ts
+++ b/tests/iso-date/DateTime.integration.test.ts
@@ -26,6 +26,10 @@ const schema = new GraphQLSchema({
         type: GraphQLDateTime,
         resolve: () => '2016-02-01T00:00:00-11:00',
       },
+      validUnixTimestamp: {
+        type: GraphQLDateTime,
+        resolve: () => 854325678,
+      },
       validUnixTimestamp: {
         type: GraphQLDateTime,
         resolve: () => 854325678000,
diff --git a/tests/iso-date/DateTime.test.ts b/tests/iso-date/DateTime.test.ts
index 8157e56c9..dbe6938ce 100644
--- a/tests/iso-date/DateTime.test.ts
+++ b/tests/iso-date/DateTime.test.ts
@@ -87,11 +87,16 @@ describe('GraphQLDateTime', () => {
     // Serializes Unix timestamp
     [
       [854325678000, '1997-01-27T00:41:18.000Z'],
-      [876535000, '1970-01-11T03:28:55.000Z'],
-      // The maximum representable unix timestamp
+      [854325678, '1997-01-27T00:41:18.000Z'],
+      [866478, '1970-01-11T00:41:18.000Z'],
+      [1713305032000, '2024-04-16T22:03:52.000Z'],
+      [1713305032, '2024-04-16T22:03:52.000Z'],
+      // The maximum representable unix timestamp in milliseconds
       [2147483647000, '2038-01-19T03:14:07.000Z'],
+      // The maximum representable unix timestamp in seconds
+      [2147483647, '2038-01-19T03:14:07.000Z'],
       // The minimum representable unit timestamp
-      [-2147483648000, '1901-12-13T20:45:52.000Z'],
+      [-2147483648, '1901-12-13T20:45:52.000Z'],
     ].forEach(([value, expected]) => {
       it(`serializes unix timestamp ${stringify(value)} into date-string ${expected}`, () => {
         expect(GraphQLDateTime.serialize(value).toJSON()).toEqual(expected);