diff --git a/README.md b/README.md
index acd6882..1a04161 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,7 @@ Node client for generating crude GraphQL specs from Swagger OpenAPI.
 | Enum                                 | ✅  |
 | ID                                   | ✅  |
 | Implements (`allOf`)                 | ✅  |
-| Polymorphism\* (`oneOf`)             | N/A |
+| Polymorphism (`oneOf`)               | ✅  |
 | Non-nullable                         | ✅  |
 | Primitives (string, boolean, number) | ✅  |
 | Query                                | 🚫  |
@@ -19,9 +19,6 @@ Node client for generating crude GraphQL specs from Swagger OpenAPI.
 
 To compare actual generated output, see the [example](./example) folder.
 
-_\* Polymorphism isn’t supported by GraphQL by design. If this encounters one
-in Swagger, it’ll assign the first type it encounters and throw a warning._
-
 ## Usage
 
 ### CLI
diff --git a/src/swagger-2.ts b/src/swagger-2.ts
index 3f00574..fcae3e8 100644
--- a/src/swagger-2.ts
+++ b/src/swagger-2.ts
@@ -43,6 +43,7 @@ function snakeCase(name: string) {
 function parse(spec: Swagger2) {
   const queue: [string, Swagger2Definition][] = [];
   const enumQueue: [string, (string | number)[]][] = [];
+  const unionQueue: [string, Swagger2Definition[]][] = [];
   const output: string[] = [];
 
   const { definitions } = spec;
@@ -87,13 +88,9 @@ function parse(spec: Swagger2) {
       return `[${TYPES[items.type]}]`;
     }
 
-    if (Array.isArray(value.oneOf)) {
-      if (value.oneOf.length > 1) {
-        console.warn(
-          `Multiple types given for ${nestedName}. Using ${JSON.stringify(value.oneOf[0])}.`
-        );
-      }
-      return getType(value.oneOf[0], '');
+    if (Array.isArray(value.oneOf) && value.oneOf.length > 0) {
+      unionQueue.push([nestedName, value.oneOf]);
+      return nestedName;
     }
 
     if (value.properties) {
@@ -123,6 +120,11 @@ function parse(spec: Swagger2) {
     output.push('}');
   }
 
+  function buildNextUnion([ID, types]: [string, Swagger2Definition[]]) {
+    const union = types.map(type => getType(type, '')).join(' | ');
+    output.push(`union ${ID} = ${union}`);
+  }
+
   function buildNextObject() {
     const nextObject = queue.pop();
     if (!nextObject) {
@@ -191,6 +193,14 @@ function parse(spec: Swagger2) {
         buildNextEnum(nextEnum);
       }
     }
+
+    // Clean up unionQueue
+    while (unionQueue.length > 0) {
+      const nextUnion = unionQueue.pop();
+      if (nextUnion) {
+        buildNextUnion(nextUnion);
+      }
+    }
   }
 
   // Begin parsing top-level entries
diff --git a/tests/swagger-2.test.ts b/tests/swagger-2.test.ts
index 3baceac..3346a0c 100644
--- a/tests/swagger-2.test.ts
+++ b/tests/swagger-2.test.ts
@@ -180,6 +180,30 @@ describe('Swagger 2 spec', () => {
 
       expect(graphqlGen(swagger)).toBe(format(graphql));
     });
+
+    it('converts oneOf to union types', () => {
+      const swagger: Swagger2 = {
+        definitions: {
+          Record: {
+            properties: {
+              rand: {
+                oneOf: [{ type: 'string' }, { type: 'integer' }],
+                type: 'array',
+              },
+            },
+            type: 'object',
+          },
+        },
+      };
+
+      const graphql = format(`
+      type Record {
+        rand: RecordRand
+      }
+      union RecordRand = String | Int`);
+
+      expect(graphqlGen(swagger)).toBe(format(graphql));
+    });
   });
 
   describe('complex structures', () => {
@@ -266,29 +290,6 @@ describe('Swagger 2 spec', () => {
 
       expect(graphqlGen(swagger)).toBe(format(graphql));
     });
-
-    it('handles oneOf (kinda)', () => {
-      const swagger: Swagger2 = {
-        definitions: {
-          Record: {
-            properties: {
-              rand: {
-                oneOf: [{ type: 'string' }, { type: 'number' }],
-                type: 'array',
-              },
-            },
-            type: 'object',
-          },
-        },
-      };
-
-      const graphql = format(`
-      type Record {
-        rand: String
-      }`);
-
-      expect(graphqlGen(swagger)).toBe(format(graphql));
-    });
   });
 
   describe('other output', () => {