diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -3853,6 +3853,9 @@
          Left.isOneOf(tok::r_square, tok::r_paren)) &&
         Right.isOneOf(tok::l_square, tok::l_paren))
       return false; // Otherwise automatic semicolon insertion would trigger.
+    if (NonComment && NonComment->is(tok::identifier) &&
+        NonComment->TokenText == "asserts")
+      return false;
     if (Left.is(TT_JsFatArrow) && Right.is(tok::l_brace))
       return false;
     if (Left.is(TT_JsTypeColon))
diff --git a/clang/unittests/Format/FormatTestJS.cpp b/clang/unittests/Format/FormatTestJS.cpp
--- a/clang/unittests/Format/FormatTestJS.cpp
+++ b/clang/unittests/Format/FormatTestJS.cpp
@@ -2589,5 +2589,20 @@
                "}\n");
 }
 
+TEST_F(FormatTestJS, NoBreakAfterAsserts) {
+  verifyFormat(
+      "interface Assertable<State extends {}> {\n"
+      "  assert<ExportedState extends {}, DependencyState extends State = "
+      "State>(\n"
+      "      callback: Callback<ExportedState, DependencyState>):\n"
+      "      asserts this is ExtendedState<DependencyState&ExportedState>;\n"
+      "}\n",
+      "interface Assertable<State extends {}> {\n"
+      "  assert<ExportedState extends {}, DependencyState extends State = "
+      "State>(callback: Callback<ExportedState, DependencyState>): asserts "
+      "this is ExtendedState<DependencyState&ExportedState>;\n"
+      "}\n");
+}
+
 } // namespace format
 } // end namespace clang