diff --git a/mlir/lib/Tools/mlir-pdll-lsp-server/MlirPdllLspServerMain.cpp b/mlir/lib/Tools/mlir-pdll-lsp-server/MlirPdllLspServerMain.cpp
--- a/mlir/lib/Tools/mlir-pdll-lsp-server/MlirPdllLspServerMain.cpp
+++ b/mlir/lib/Tools/mlir-pdll-lsp-server/MlirPdllLspServerMain.cpp
@@ -51,6 +51,10 @@
       llvm::cl::desc("Pretty-print JSON output"),
       llvm::cl::init(false),
   };
+  llvm::cl::list<std::string> extraIncludeDirs(
+      "I", llvm::cl::desc("Extra directory of include files"),
+      llvm::cl::value_desc("directory"), llvm::cl::Prefix);
+
   llvm::cl::ParseCommandLineOptions(argc, argv, "MLIR LSP Language Server");
 
   if (litTest) {
@@ -67,6 +71,7 @@
   JSONTransport transport(stdin, llvm::outs(), inputStyle, prettyPrint);
 
   // Configure the servers and start the main language server.
-  PDLLServer server;
+  PDLLServer::Options options(extraIncludeDirs);
+  PDLLServer server(options);
   return runPdllLSPServer(server, transport);
 }
diff --git a/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.h b/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.h
--- a/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.h
+++ b/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.h
@@ -28,7 +28,14 @@
 /// separate from the logic that involves LSP server/client communication.
 class PDLLServer {
 public:
-  PDLLServer();
+  struct Options {
+    Options(const std::vector<std::string> &extraDirs) : extraDirs(extraDirs){};
+
+    /// Additional list of include directories to search.
+    const std::vector<std::string> &extraDirs;
+  };
+
+  PDLLServer(const Options &options);
   ~PDLLServer();
 
   /// Add or update the document, with the provided `version`, at the given URI.
@@ -68,8 +75,10 @@
                                  const Position &helpPos);
 
 private:
-  struct Impl;
+  /// PDLL LSP options.
+  const Options &options;
 
+  struct Impl;
   std::unique_ptr<Impl> impl;
 };
 
diff --git a/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.cpp b/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.cpp
--- a/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.cpp
+++ b/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.cpp
@@ -238,6 +238,7 @@
 /// document.
 struct PDLDocument {
   PDLDocument(const lsp::URIForFile &uri, StringRef contents,
+              const std::vector<std::string> &extraDirs,
               std::vector<lsp::Diagnostic> &diagnostics);
   PDLDocument(const PDLDocument &) = delete;
   PDLDocument &operator=(const PDLDocument &) = delete;
@@ -315,6 +316,7 @@
 } // namespace
 
 PDLDocument::PDLDocument(const lsp::URIForFile &uri, StringRef contents,
+                         const std::vector<std::string> &extraDirs,
                          std::vector<lsp::Diagnostic> &diagnostics)
     : astContext(odsContext) {
   auto memBuffer = llvm::MemoryBuffer::getMemBufferCopy(contents, uri.file());
@@ -327,6 +329,7 @@
   llvm::SmallString<32> uriDirectory(uri.file());
   llvm::sys::path::remove_filename(uriDirectory);
   includeDirs.push_back(uriDirectory.str().str());
+  includeDirs.insert(includeDirs.end(), extraDirs.begin(), extraDirs.end());
 
   sourceMgr.setIncludeDirs(includeDirs);
   sourceMgr.AddNewSourceBuffer(std::move(memBuffer), SMLoc());
@@ -991,8 +994,10 @@
 struct PDLTextFileChunk {
   PDLTextFileChunk(uint64_t lineOffset, const lsp::URIForFile &uri,
                    StringRef contents,
+                   const std::vector<std::string> &extraDirs,
                    std::vector<lsp::Diagnostic> &diagnostics)
-      : lineOffset(lineOffset), document(uri, contents, diagnostics) {}
+      : lineOffset(lineOffset),
+        document(uri, contents, extraDirs, diagnostics) {}
 
   /// Adjust the line number of the given range to anchor at the beginning of
   /// the file, instead of the beginning of this chunk.
@@ -1020,7 +1025,8 @@
 class PDLTextFile {
 public:
   PDLTextFile(const lsp::URIForFile &uri, StringRef fileContents,
-              int64_t version, std::vector<lsp::Diagnostic> &diagnostics);
+              int64_t version, const std::vector<std::string> &extraDirs,
+              std::vector<lsp::Diagnostic> &diagnostics);
 
   /// Return the current version of this text file.
   int64_t getVersion() const { return version; }
@@ -1064,6 +1070,7 @@
 
 PDLTextFile::PDLTextFile(const lsp::URIForFile &uri, StringRef fileContents,
                          int64_t version,
+                         const std::vector<std::string> &extraDirs,
                          std::vector<lsp::Diagnostic> &diagnostics)
     : contents(fileContents.str()), version(version), totalNumLines(0) {
   // Split the file into separate PDL documents.
@@ -1073,13 +1080,13 @@
   SmallVector<StringRef, 8> subContents;
   StringRef(contents).split(subContents, "// -----");
   chunks.emplace_back(std::make_unique<PDLTextFileChunk>(
-      /*lineOffset=*/0, uri, subContents.front(), diagnostics));
+      /*lineOffset=*/0, uri, subContents.front(), extraDirs, diagnostics));
 
   uint64_t lineOffset = subContents.front().count('\n');
   for (StringRef docContents : llvm::drop_begin(subContents)) {
     unsigned currentNumDiags = diagnostics.size();
-    auto chunk = std::make_unique<PDLTextFileChunk>(lineOffset, uri,
-                                                    docContents, diagnostics);
+    auto chunk = std::make_unique<PDLTextFileChunk>(
+        lineOffset, uri, docContents, extraDirs, diagnostics);
     lineOffset += docContents.count('\n');
 
     // Adjust locations used in diagnostics to account for the offset from the
@@ -1226,14 +1233,15 @@
 // PDLLServer
 //===----------------------------------------------------------------------===//
 
-lsp::PDLLServer::PDLLServer() : impl(std::make_unique<Impl>()) {}
+lsp::PDLLServer::PDLLServer(const Options &options)
+    : options(options), impl(std::make_unique<Impl>()) {}
 lsp::PDLLServer::~PDLLServer() = default;
 
 void lsp::PDLLServer::addOrUpdateDocument(
     const URIForFile &uri, StringRef contents, int64_t version,
     std::vector<Diagnostic> &diagnostics) {
-  impl->files[uri.file()] =
-      std::make_unique<PDLTextFile>(uri, contents, version, diagnostics);
+  impl->files[uri.file()] = std::make_unique<PDLTextFile>(
+      uri, contents, version, options.extraDirs, diagnostics);
 }
 
 Optional<int64_t> lsp::PDLLServer::removeDocument(const URIForFile &uri) {