diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -324,12 +324,21 @@
 }
 
 void UnwrappedLineParser::parseCSharpAttribute() {
+  int UnpairedSquareBrackets = 1;
   do {
     switch (FormatTok->Tok.getKind()) {
     case tok::r_square:
       nextToken();
-      addUnwrappedLine();
-      return;
+      --UnpairedSquareBrackets;
+      if (UnpairedSquareBrackets == 0) {
+        addUnwrappedLine();
+        return;
+      }
+      break;
+    case tok::l_square:
+      ++UnpairedSquareBrackets;
+      nextToken();
+      break;
     default:
       nextToken();
       break;
diff --git a/clang/unittests/Format/FormatTestCSharp.cpp b/clang/unittests/Format/FormatTestCSharp.cpp
--- a/clang/unittests/Format/FormatTestCSharp.cpp
+++ b/clang/unittests/Format/FormatTestCSharp.cpp
@@ -273,6 +273,15 @@
                "{\n"
                "}");
 
+  // [] in an attribute do not cause premature line wrapping or indenting.
+  verifyFormat(R"(//
+public class A
+{
+    [SomeAttribute(new[] { RED, GREEN, BLUE }, -1.0f, 1.0f)]
+    [DoNotSerialize]
+    public Data MemberVariable;
+})");
+
   //  Unwrappable lines go on a line of their own.
   // 'target:' is not treated as a label.
   // Modify Style to enforce a column limit.