diff --git a/src/printer-graphql.js b/src/printer-graphql.js
index 33540a0f0..a45c83d4a 100644
--- a/src/printer-graphql.js
+++ b/src/printer-graphql.js
@@ -4,6 +4,7 @@ const docBuilders = require("./doc-builders");
 const concat = docBuilders.concat;
 const join = docBuilders.join;
 const hardline = docBuilders.hardline;
+const line = docBuilders.line;
 const softline = docBuilders.softline;
 const group = docBuilders.group;
 const indent = docBuilders.indent;
@@ -225,6 +226,23 @@ function genericPrint(path, options, print) {
       ]);
     }
 
+    case "UnionTypeDefinition": {
+      return group(
+        concat([
+          "union ",
+          path.call(print, "name"),
+          " =",
+          ifBreak("", " "),
+          indent(
+            concat([
+              ifBreak(concat([line, "  "])),
+              join(concat([line, "| "]), path.map(print, "types"))
+            ])
+          )
+        ])
+      );
+    }
+
     default:
       throw new Error("unknown graphql type: " + JSON.stringify(n.kind));
   }
diff --git a/tests/graphql_union_types/__snapshots__/jsfmt.spec.js.snap b/tests/graphql_union_types/__snapshots__/jsfmt.spec.js.snap
new file mode 100644
index 000000000..016a74fc9
--- /dev/null
+++ b/tests/graphql_union_types/__snapshots__/jsfmt.spec.js.snap
@@ -0,0 +1,56 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`union_types.graphql 1`] = `
+union myUnion = ATypeName | ASecondTypeName
+
+union tooLongNameeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee = A | B
+
+union mySecondUnion = ATypeName | ASecondTypeName | AThirdTypeName
+
+union myThirdUnion = AVeryVeryVeryLongNamedTypeName | ASecondVeryVeryVeryLongedNameTypeName 
+
+union longUnion = A | B | C | D | E | F | G | H | I | J | K | L |  A | B | C | D | E | F | G | H | I | J | K | L
+
+# comment
+# comment2
+union union = B | C | D~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+union myUnion = ATypeName | ASecondTypeName
+
+union tooLongNameeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee =
+    A
+  | B
+
+union mySecondUnion = ATypeName | ASecondTypeName | AThirdTypeName
+
+union myThirdUnion =
+    AVeryVeryVeryLongNamedTypeName
+  | ASecondVeryVeryVeryLongedNameTypeName
+
+union longUnion =
+    A
+  | B
+  | C
+  | D
+  | E
+  | F
+  | G
+  | H
+  | I
+  | J
+  | K
+  | L
+  | A
+  | B
+  | C
+  | D
+  | E
+  | F
+  | G
+  | H
+  | I
+  | J
+  | K
+  | L
+
+union union = B | C | D
+`;
diff --git a/tests/graphql_union_types/jsfmt.spec.js b/tests/graphql_union_types/jsfmt.spec.js
new file mode 100644
index 000000000..335646fb2
--- /dev/null
+++ b/tests/graphql_union_types/jsfmt.spec.js
@@ -0,0 +1 @@
+run_spec(__dirname, { parser: "graphql" });
diff --git a/tests/graphql_union_types/union_types.graphql b/tests/graphql_union_types/union_types.graphql
new file mode 100644
index 000000000..6823a860a
--- /dev/null
+++ b/tests/graphql_union_types/union_types.graphql
@@ -0,0 +1,13 @@
+union myUnion = ATypeName | ASecondTypeName
+
+union tooLongNameeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee = A | B
+
+union mySecondUnion = ATypeName | ASecondTypeName | AThirdTypeName
+
+union myThirdUnion = AVeryVeryVeryLongNamedTypeName | ASecondVeryVeryVeryLongedNameTypeName 
+
+union longUnion = A | B | C | D | E | F | G | H | I | J | K | L |  A | B | C | D | E | F | G | H | I | J | K | L
+
+# comment
+# comment2
+union union = B | C | D
\ No newline at end of file