diff --git a/clang/lib/CAS/IncludeTree.cpp b/clang/lib/CAS/IncludeTree.cpp
index 8cb2ad4c2de7d..3613bd478328c 100644
--- a/clang/lib/CAS/IncludeTree.cpp
+++ b/clang/lib/CAS/IncludeTree.cpp
@@ -1039,6 +1039,26 @@ class IncludeTreeFileSystem final : public llvm::cas::CASBackedFileSystem {
   createThreadSafeProxyFS() override {
     llvm::report_fatal_error("not implemented");
   }
+
+  void printImpl(raw_ostream &OS, PrintType Type,
+                 unsigned IndentLevel) const final {
+    printIndent(OS, IndentLevel);
+    IndentLevel += 1;
+    OS << "IncludeTreeFileSystem\n";
+    if (Type == PrintType::Summary)
+      return;
+
+    // Files is unordered, so sort by name to get a deterministic order.
+    std::vector<std::pair<StringRef, ObjectRef>> FileRefs;
+    for (auto &[Name, F] : Files)
+      FileRefs.emplace_back(Name, F.ContentsRef);
+    llvm::sort(FileRefs, [](auto &&A, auto &&B) { return A.first < B.first; });
+
+    for (auto &[Name, ContentsRef] : FileRefs) {
+      printIndent(OS, IndentLevel);
+      OS << Name << ' ' << CAS.getID(ContentsRef) << '\n';
+    }
+  }
 };
 } // namespace
 
diff --git a/clang/unittests/CAS/IncludeTreeTest.cpp b/clang/unittests/CAS/IncludeTreeTest.cpp
index 88b68a523043f..cad02ac228226 100644
--- a/clang/unittests/CAS/IncludeTreeTest.cpp
+++ b/clang/unittests/CAS/IncludeTreeTest.cpp
@@ -296,27 +296,29 @@ TEST(IncludeTree, IncludeTreeFileListDuplicates) {
   EXPECT_EQ(I, Files.size());
 }
 
-TEST(IncludeTree, IncludeTreeFileSystemOverlay) {
-  StringRef PathSep = llvm::sys::path::get_separator();
-  std::shared_ptr<ObjectStore> DB = llvm::cas::createInMemoryCAS();
+static Expected<IntrusiveRefCntPtr<llvm::vfs::FileSystem>>
+createTestInclueTreeFS(ObjectStore &DB, unsigned NumFiles = 10) {
   SmallVector<IncludeTree::FileList::FileEntry> Files;
-  for (unsigned I = 0; I < 10; ++I) {
+  for (unsigned I = 0; I < NumFiles; ++I) {
     std::optional<IncludeTree::File> File;
     std::string Path = "/file" + std::to_string(I);
     static constexpr StringRef Bytes = "123456789";
     std::optional<ObjectRef> Content;
-    ASSERT_THAT_ERROR(
-        DB->storeFromString({}, Bytes.substr(0, I)).moveInto(Content),
-        llvm::Succeeded());
-    ASSERT_THAT_ERROR(
-        IncludeTree::File::create(*DB, Path, *Content).moveInto(File),
-        llvm::Succeeded());
+    if (auto E = DB.storeFromString({}, Bytes.substr(0, I)).moveInto(Content))
+      return std::move(E);
+    if (auto E = IncludeTree::File::create(DB, Path, *Content).moveInto(File))
+      return std::move(E);
     Files.push_back({File->getRef(), I});
   }
+  return createIncludeTreeFileSystem(DB, Files);
+}
+
+TEST(IncludeTree, IncludeTreeFileSystemOverlay) {
+  StringRef PathSep = llvm::sys::path::get_separator();
+  std::shared_ptr<ObjectStore> DB = llvm::cas::createInMemoryCAS();
   IntrusiveRefCntPtr<llvm::vfs::FileSystem> IncludeTreeFS;
-  ASSERT_THAT_ERROR(
-      createIncludeTreeFileSystem(*DB, Files).moveInto(IncludeTreeFS),
-      llvm::Succeeded());
+  ASSERT_THAT_ERROR(createTestInclueTreeFS(*DB).moveInto(IncludeTreeFS),
+                    llvm::Succeeded());
 
   auto FS = llvm::makeIntrusiveRefCnt<llvm::vfs::InMemoryFileSystem>();
   FS->setCurrentWorkingDirectory("/dir");
@@ -338,3 +340,32 @@ TEST(IncludeTree, IncludeTreeFileSystemOverlay) {
   }
   ASSERT_EQ(NumFile, 2);
 }
+
+TEST(IncludeTree, IncludeTreeFileSystemPrint) {
+  std::shared_ptr<ObjectStore> DB = llvm::cas::createInMemoryCAS();
+  IntrusiveRefCntPtr<llvm::vfs::FileSystem> IncludeTreeFS;
+  ASSERT_THAT_ERROR(
+      createTestInclueTreeFS(*DB, /*NumFiles=*/3).moveInto(IncludeTreeFS),
+      llvm::Succeeded());
+
+  {
+    std::string FSStr;
+    llvm::raw_string_ostream OS(FSStr);
+    IncludeTreeFS->print(OS, llvm::vfs::FileSystem::PrintType::Summary);
+    EXPECT_EQ(FSStr, "IncludeTreeFileSystem\n");
+  }
+  {
+    std::string FSStr;
+    llvm::raw_string_ostream OS(FSStr);
+    IncludeTreeFS->print(OS, llvm::vfs::FileSystem::PrintType::Contents);
+    StringRef Printed(FSStr);
+    EXPECT_TRUE(Printed.consume_front("IncludeTreeFileSystem")) << Printed;
+    EXPECT_TRUE(Printed.consume_front("\n  /file0 llvmcas://")) << Printed;
+    Printed = Printed.drop_front(64); // 32 hash bytes in hex
+    EXPECT_TRUE(Printed.consume_front("\n  /file1 llvmcas://")) << Printed;
+    Printed = Printed.drop_front(64); // 32 hash bytes in hex
+    EXPECT_TRUE(Printed.consume_front("\n  /file2 llvmcas://")) << Printed;
+    Printed = Printed.drop_front(64); // 32 hash bytes in hex
+    EXPECT_EQ(Printed, "\n");         // Final newline.
+  }
+}
diff --git a/llvm/lib/CAS/CASFileSystem.cpp b/llvm/lib/CAS/CASFileSystem.cpp
index 4485498bbad8f..83749d19652a1 100644
--- a/llvm/lib/CAS/CASFileSystem.cpp
+++ b/llvm/lib/CAS/CASFileSystem.cpp
@@ -96,6 +96,9 @@ class CASFileSystem final
     return WorkingDirectory.Path;
   }
 
+  void printImpl(raw_ostream &OS, PrintType Type,
+                 unsigned IndentLevel) const final;
+
   Error initialize(ObjectRef Root);
 
   CASFileSystem(std::shared_ptr<ObjectStore> DB, sys::path::Style PathStyle)
@@ -184,6 +187,45 @@ std::error_code CASFileSystem::setCurrentWorkingDirectory(const Twine &Path) {
   return std::error_code();
 }
 
+void CASFileSystem::printImpl(raw_ostream &OS, PrintType Type,
+                              unsigned IndentLevel) const {
+  printIndent(OS, IndentLevel);
+  OS << "CASFileSystem\n";
+  if (Type == PrintType::Summary)
+    return;
+
+  IndentLevel += 1;
+  printIndent(OS, IndentLevel);
+  StringRef path_separator = get_separator(PathStyle);
+  auto &Root = Cache->getRoot(path_separator);
+  OS << "root: " << Root.getTreePath();
+  assert(Root.getRef() && "missing ID for primary CASFileSystem root");
+  if (Root.getRef())
+    OS << ' ' << DB.getID(*Root.getRef()) << '\n';
+
+  if (Type == PrintType::Contents)
+    return;
+
+  IndentLevel += 1;
+  TreeSchema Schema(DB);
+  auto TreeN = DB.getProxy(*Root.getRef());
+  if (!TreeN) {
+    OS << toString(TreeN.takeError()) << '\n';
+    return;
+  }
+  Error E = Schema.walkFileTreeRecursively(
+      DB, TreeN->getRef(),
+      [&](const NamedTreeEntry &Entry, std::optional<TreeProxy> Tree) -> Error {
+        if (Entry.getKind() != TreeEntry::Tree) {
+          printIndent(OS, IndentLevel);
+          Entry.print(OS, DB);
+        }
+        return Error::success();
+      });
+  if (E)
+    OS << toString(std::move(E)) << '\n';
+}
+
 Error CASFileSystem::loadDirectory(DirectoryEntry &Parent) {
   Directory &D = Parent.asDirectory();
   if (D.isComplete())
diff --git a/llvm/lib/CAS/CachingOnDiskFileSystem.cpp b/llvm/lib/CAS/CachingOnDiskFileSystem.cpp
index 3b9c6089fcbb3..c04abc8785939 100644
--- a/llvm/lib/CAS/CachingOnDiskFileSystem.cpp
+++ b/llvm/lib/CAS/CachingOnDiskFileSystem.cpp
@@ -121,6 +121,9 @@ class CachingOnDiskFileSystemImpl final : public CachingOnDiskFileSystem {
     return makeIntrusiveRefCnt<CachingOnDiskFileSystemImpl>(*this);
   }
 
+  void printImpl(raw_ostream &OS, PrintType Type,
+                 unsigned IndentLevel) const final;
+
   CachingOnDiskFileSystemImpl(std::shared_ptr<ObjectStore> DB)
       : CachingOnDiskFileSystem(std::move(DB)) {
     initializeWorkingDirectory();
@@ -894,6 +897,13 @@ CachingOnDiskFileSystemImpl::createTreeBuilder() {
   return std::make_unique<TreeBuilder>(*this);
 }
 
+void CachingOnDiskFileSystemImpl::printImpl(raw_ostream &OS, PrintType Type,
+                                            unsigned IndentLevel) const {
+  printIndent(OS, IndentLevel);
+  OS << "CachingOnDiskFileSystem\n";
+  // FIXME: print contents
+}
+
 void CachingOnDiskFileSystemImpl::TreeBuilder::pushSymlink(
     const DirectoryEntry &Entry) {
   assert(Entry.isSymlink());
diff --git a/llvm/unittests/CAS/CASFileSystemTest.cpp b/llvm/unittests/CAS/CASFileSystemTest.cpp
index ad6342baa5499..714d54de2d148 100644
--- a/llvm/unittests/CAS/CASFileSystemTest.cpp
+++ b/llvm/unittests/CAS/CASFileSystemTest.cpp
@@ -516,3 +516,46 @@ TEST(CASFileSystemTest, recursiveDirectoryIteratorNested) {
                                             sys::fs::file_type::regular_file));
   ASSERT_TRUE(isEnd(D, EC));
 }
+
+TEST(CASFileSystemTest, print) {
+  std::unique_ptr<ObjectStore> CAS = createInMemoryCAS();
+  ASSERT_TRUE(CAS);
+  std::optional<ObjectProxy> Tree;
+  ASSERT_THAT_ERROR(createNestedTree(*CAS).moveInto(Tree), Succeeded());
+  std::unique_ptr<vfs::FileSystem> CASFS;
+  ASSERT_THAT_ERROR(createFS(*CAS, *Tree).moveInto(CASFS), Succeeded());
+
+  {
+    std::string FSStr;
+    llvm::raw_string_ostream OS(FSStr);
+    CASFS->print(OS, vfs::FileSystem::PrintType::Summary);
+    EXPECT_EQ(FSStr, "CASFileSystem\n");
+  }
+  {
+    std::string FSStr;
+    llvm::raw_string_ostream OS(FSStr);
+    CASFS->print(OS, vfs::FileSystem::PrintType::Contents);
+    std::string Expected = "CASFileSystem\n";
+    Expected += "  root: / " + Tree->getID().toString() + "\n";
+    EXPECT_EQ(FSStr, Expected);
+  }
+  {
+    std::string FSStr;
+    llvm::raw_string_ostream OS(FSStr);
+    CASFS->print(OS, vfs::FileSystem::PrintType::RecursiveContents);
+    std::string Expected = "CASFileSystem\n";
+    Expected += "  root: / " + Tree->getID().toString() + "\n";
+    StringRef Printed(FSStr);
+    EXPECT_TRUE(Printed.consume_front("CASFileSystem")) << Printed;
+    EXPECT_TRUE(Printed.consume_front("\n  root: / llvmcas://")) << Printed;
+    Printed = Printed.drop_front(64); // 32 hash bytes in hex
+    EXPECT_TRUE(Printed.consume_front("\n    file llvmcas://")) << Printed;
+    Printed = Printed.drop_front(64); // 32 hash bytes in hex
+    EXPECT_TRUE(Printed.consume_front(" /d2")) << Printed;
+    EXPECT_TRUE(Printed.consume_front("\n    file llvmcas://")) << Printed;
+    Printed = Printed.drop_front(64); // 32 hash bytes in hex
+    EXPECT_TRUE(Printed.consume_front(" /t1/d1\n")) << Printed;
+    // ...
+    EXPECT_TRUE(Printed.consume_back("/t3/t2/d2\n")) << Printed;
+  }
+}