diff --git a/clang-tools-extra/CMakeLists.txt b/clang-tools-extra/CMakeLists.txt
index 6b6f2b1ca2276..7ff17fa489693 100644
--- a/clang-tools-extra/CMakeLists.txt
+++ b/clang-tools-extra/CMakeLists.txt
@@ -25,6 +25,7 @@ add_subdirectory(clang-doc)
 add_subdirectory(clang-include-fixer)
 add_subdirectory(clang-move)
 add_subdirectory(clang-query)
+add_subdirectory(clang-read-diagnostics)
 add_subdirectory(include-cleaner)
 add_subdirectory(pp-trace)
 add_subdirectory(tool-template)
diff --git a/clang-tools-extra/clang-read-diagnostics/CMakeLists.txt b/clang-tools-extra/clang-read-diagnostics/CMakeLists.txt
new file mode 100644
index 0000000000000..922465ad3e098
--- /dev/null
+++ b/clang-tools-extra/clang-read-diagnostics/CMakeLists.txt
@@ -0,0 +1,8 @@
+add_clang_tool(clang-read-diagnostics
+  ClangReadDiagnostics.cpp
+  )
+
+clang_target_link_libraries(clang-read-diagnostics
+  PRIVATE
+  clangFrontend
+  )
diff --git a/clang-tools-extra/clang-read-diagnostics/ClangReadDiagnostics.cpp b/clang-tools-extra/clang-read-diagnostics/ClangReadDiagnostics.cpp
new file mode 100644
index 0000000000000..6dd7fd532b0ab
--- /dev/null
+++ b/clang-tools-extra/clang-read-diagnostics/ClangReadDiagnostics.cpp
@@ -0,0 +1,129 @@
+//===---- ClangReadDiagnostics.cpp - clang-read-diagnostics tool ----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This tool is for reading clang diagnostics files from -serialize-diagnostics.
+//
+// Example usage:
+//
+// $ clang -serialize-diagnostics foo.c.diag foo.c
+// $ clang-read-diagnostics foo.c.diag
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Frontend/SerializedDiagnosticReader.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Signals.h"
+
+#include <string>
+
+using namespace clang;
+using namespace clang::serialized_diags;
+using namespace llvm;
+
+static cl::list<std::string> InputFiles(cl::Sink, cl::desc("<input files...>"),
+                                        cl::Required);
+
+class BasicSerializedDiagnosticReader : public SerializedDiagnosticReader {
+public:
+  struct DecodedDiagnostics {
+    unsigned Severity;
+    StringRef Filename;
+    unsigned Line;
+    unsigned Col;
+    StringRef Category;
+    StringRef Flag;
+    StringRef Message;
+  };
+
+  SmallVector<DecodedDiagnostics> getDiagnostics() {
+    SmallVector<DecodedDiagnostics> Ret;
+    for (const auto &Diag : Diagnostics_) {
+      auto Filename = FilenameIdx_.at(Diag.Location.FileID);
+      auto Category = CategoryIdx_.at(Diag.Category);
+      auto Flag = Diag.Flag == 0 ? "" : FlagIdx_.at(Diag.Flag);
+      Ret.emplace_back(DecodedDiagnostics{Diag.Severity, Filename,
+                                          Diag.Location.Line, Diag.Location.Col,
+                                          Category, Flag, Diag.Message});
+    }
+    return Ret;
+  }
+
+  void dump() {
+    for (const auto &Diag : getDiagnostics()) {
+      llvm::dbgs() << Diag.Filename << ":" << Diag.Line << ":" << Diag.Col
+                   << ": " << Diag.Message << " [category=\'" << Diag.Category
+                   << "'";
+
+      if (!Diag.Flag.empty())
+        llvm::dbgs() << ", flag=" << Diag.Flag;
+
+      llvm::dbgs() << "]" << "\n";
+    }
+  }
+
+protected:
+  virtual std::error_code visitCategoryRecord(unsigned ID,
+                                              StringRef Name) override {
+    const auto &[_, Inserted] = CategoryIdx_.try_emplace(ID, Name);
+    assert(Inserted && "duplicate IDs");
+    return {};
+  }
+
+  virtual std::error_code visitDiagFlagRecord(unsigned ID,
+                                              StringRef Name) override {
+    const auto &[_, Inserted] = FlagIdx_.try_emplace(ID, Name);
+    assert(Inserted && "duplicate IDs");
+    return {};
+  }
+
+  virtual std::error_code visitFilenameRecord(unsigned ID, unsigned Size,
+                                              unsigned Timestamp,
+                                              StringRef Name) override {
+    const auto &[_, Inserted] = FilenameIdx_.try_emplace(ID, Name);
+    assert(Inserted && "duplicate IDs");
+    return {};
+  }
+
+  virtual std::error_code visitDiagnosticRecord(unsigned Severity,
+                                                const Location &Location,
+                                                unsigned Category,
+                                                unsigned Flag,
+                                                StringRef Message) override {
+    Diagnostics_.emplace_back(
+        RawDiagnostic{Severity, Location, Category, Flag, Message});
+    return {};
+  }
+
+private:
+  struct RawDiagnostic {
+    unsigned Severity;
+    Location Location;
+    unsigned Category;
+    unsigned Flag;
+    StringRef Message;
+  };
+
+  DenseMap<unsigned, StringRef> CategoryIdx_;
+  DenseMap<unsigned, StringRef> FlagIdx_;
+  DenseMap<unsigned, StringRef> FilenameIdx_;
+  std::vector<RawDiagnostic> Diagnostics_;
+};
+
+int main(int argc, const char **argv) {
+  cl::ParseCommandLineOptions(argc, argv);
+  llvm::sys::PrintStackTraceOnErrorSignal(argv[0]);
+
+  for (const auto &File : InputFiles) {
+    BasicSerializedDiagnosticReader BSDR{};
+    BSDR.readDiagnostics(File);
+    BSDR.dump();
+  }
+
+  return 0;
+}
diff --git a/clang-tools-extra/test/CMakeLists.txt b/clang-tools-extra/test/CMakeLists.txt
index 7e4d99d8cfc1d..84426c9a56b7f 100644
--- a/clang-tools-extra/test/CMakeLists.txt
+++ b/clang-tools-extra/test/CMakeLists.txt
@@ -38,6 +38,7 @@ set(CLANG_TOOLS_TEST_DEPS
   clang-include-fixer
   clang-move
   clang-query
+  clang-read-diagnostics
   clang-reorder-fields
   find-all-symbols
   modularize
diff --git a/clang-tools-extra/test/clang-read-diagnostics/error_and_warning.c b/clang-tools-extra/test/clang-read-diagnostics/error_and_warning.c
new file mode 100644
index 0000000000000..5d9263f2dea72
--- /dev/null
+++ b/clang-tools-extra/test/clang-read-diagnostics/error_and_warning.c
@@ -0,0 +1,14 @@
+// REQUIRES: clang
+// RUN: not %clang %s -serialize-diagnostics %t
+// RUN: clang-read-diagnostics %t 2>&1 | FileCheck %s
+
+#include <stdio.h>
+
+int forgot_return() {
+  // CHECK: error_and_warning.c:9:1: non-void function does not return a value [category='Semantic Issue', flag=return-type]
+}
+
+int main() {
+  // CHECK: error_and_warning.c:13:25: expected ';' after expression [category='Parse Issue']
+  printf("Hello world!")
+}