diff --git a/clang-tools-extra/clangd/index/remote/server/Server.cpp b/clang-tools-extra/clangd/index/remote/server/Server.cpp
--- a/clang-tools-extra/clangd/index/remote/server/Server.cpp
+++ b/clang-tools-extra/clangd/index/remote/server/Server.cpp
@@ -39,6 +39,15 @@
 llvm::cl::opt<std::string> IndexRoot(llvm::cl::desc("<PROJECT ROOT>"),
                                      llvm::cl::Positional, llvm::cl::Required);
 
+llvm::cl::opt<Logger::Level> LogLevel{
+    "log",
+    llvm::cl::desc("Verbosity of log messages written to stderr"),
+    values(clEnumValN(Logger::Error, "error", "Error messages only"),
+           clEnumValN(Logger::Info, "info", "High level execution tracing"),
+           clEnumValN(Logger::Debug, "verbose", "Low level details")),
+    llvm::cl::init(Logger::Info),
+};
+
 llvm::cl::opt<std::string> TraceFile(
     "trace-file",
     llvm::cl::desc("Path to the file where tracer logs will be stored"));
@@ -173,7 +182,7 @@
   Builder.AddListeningPort(ServerAddress, grpc::InsecureServerCredentials());
   Builder.RegisterService(&Service);
   std::unique_ptr<grpc::Server> Server(Builder.BuildAndStart());
-  llvm::outs() << "Server listening on " << ServerAddress << '\n';
+  log("Server listening on {0}", ServerAddress);
 
   Server->Wait();
 }
@@ -191,10 +200,16 @@
   llvm::sys::PrintStackTraceOnErrorSignal(argv[0]);
 
   if (!llvm::sys::path::is_absolute(IndexRoot)) {
-    elog("Index root should be an absolute path.");
+    llvm::errs() << "Index root should be an absolute path.\n";
     return -1;
   }
 
+  llvm::errs().SetBuffered();
+  // Don't flush stdout when logging for thread safety.
+  llvm::errs().tie(nullptr);
+  clang::clangd::StreamLogger Logger(llvm::errs(), LogLevel);
+  clang::clangd::LoggingSession LoggingSession(Logger);
+
   llvm::Optional<llvm::raw_fd_ostream> TracerStream;
   std::unique_ptr<clang::clangd::trace::EventTracer> Tracer;
   if (!TraceFile.empty()) {
@@ -220,7 +235,7 @@
   std::unique_ptr<clang::clangd::SymbolIndex> Index = openIndex(IndexPath);
 
   if (!Index) {
-    elog("Failed to open the index.");
+    llvm::errs() << "Failed to open the index.\n";
     return -1;
   }
 
diff --git a/clang-tools-extra/clangd/indexer/IndexerMain.cpp b/clang-tools-extra/clangd/indexer/IndexerMain.cpp
--- a/clang-tools-extra/clangd/indexer/IndexerMain.cpp
+++ b/clang-tools-extra/clangd/indexer/IndexerMain.cpp
@@ -16,6 +16,7 @@
 #include "index/Serialization.h"
 #include "index/Symbol.h"
 #include "index/SymbolCollector.h"
+#include "support/Logger.h"
 #include "clang/Tooling/ArgumentsAdjusters.h"
 #include "clang/Tooling/CommonOptionsParser.h"
 #include "clang/Tooling/Execution.h"
@@ -122,7 +123,7 @@
       std::make_unique<clang::clangd::IndexActionFactory>(Data),
       clang::tooling::getStripPluginsAdjuster());
   if (Err) {
-    llvm::errs() << llvm::toString(std::move(Err)) << "\n";
+    clang::clangd::elog("{0}", std::move(Err));
   }
 
   // Emit collected data.
diff --git a/clang-tools-extra/clangd/tool/ClangdMain.cpp b/clang-tools-extra/clangd/tool/ClangdMain.cpp
--- a/clang-tools-extra/clangd/tool/ClangdMain.cpp
+++ b/clang-tools-extra/clangd/tool/ClangdMain.cpp
@@ -657,16 +657,16 @@
       // continuing.
       llvm::SmallString<128> Path(CompileCommandsDir);
       if (std::error_code EC = llvm::sys::fs::make_absolute(Path)) {
-        llvm::errs() << "Error while converting the relative path specified by "
-                        "--compile-commands-dir to an absolute path: "
-                     << EC.message() << ". The argument will be ignored.\n";
+        elog("Error while converting the relative path specified by "
+             "--compile-commands-dir to an absolute path: {0}. The argument "
+             "will be ignored.",
+             EC.message());
       } else {
         CompileCommandsDirPath = std::string(Path.str());
       }
     } else {
-      llvm::errs()
-          << "Path specified by --compile-commands-dir does not exist. The "
-             "argument will be ignored.\n";
+      elog("Path specified by --compile-commands-dir does not exist. The "
+           "argument will be ignored.");
     }
   }
 
@@ -750,7 +750,7 @@
       elog("Couldn't determine user config file, not loading");
     }
     std::vector<const config::Provider *> ProviderPointers;
-    for (const auto& P : ProviderStack)
+    for (const auto &P : ProviderStack)
       ProviderPointers.push_back(P.get());
     Config = config::Provider::combine(std::move(ProviderPointers));
     Opts.ConfigProvider = Config.get();