diff --git a/packages/babel-generator/src/generators/methods.js b/packages/babel-generator/src/generators/methods.js
index e9d0c67bded7..ea656b8b0c1f 100644
--- a/packages/babel-generator/src/generators/methods.js
+++ b/packages/babel-generator/src/generators/methods.js
@@ -37,6 +37,8 @@ export function _methodHead(node: Object) {
   }
 
   if (node.async) {
+    // ensure `async` is in the same line with property name
+    this._catchUp("start", key.loc);
     this.word("async");
     this.space();
   }
diff --git a/packages/babel-generator/test/fixtures/regression/11870/input.js b/packages/babel-generator/test/fixtures/regression/11870/input.js
new file mode 100644
index 000000000000..810351d6e237
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/regression/11870/input.js
@@ -0,0 +1,4 @@
+class Test {
+  @TestDecorator
+  async decorateMe() {}
+}
diff --git a/packages/babel-generator/test/fixtures/regression/11870/options.json b/packages/babel-generator/test/fixtures/regression/11870/options.json
new file mode 100644
index 000000000000..f60ee7d59843
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/regression/11870/options.json
@@ -0,0 +1,4 @@
+{
+  "retainLines": true,
+  "plugins": [["decorators", { "decoratorsBeforeExport": true }]]
+}
diff --git a/packages/babel-generator/test/fixtures/regression/11870/output.js b/packages/babel-generator/test/fixtures/regression/11870/output.js
new file mode 100644
index 000000000000..7dee47804925
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/regression/11870/output.js
@@ -0,0 +1,3 @@
+class Test {
+  @TestDecorator
+  async decorateMe() {}}
\ No newline at end of file