diff --git a/src/message_handler.cc b/src/message_handler.cc
index 498a72de..09ee6cbf 100644
--- a/src/message_handler.cc
+++ b/src/message_handler.cc
@@ -28,6 +28,7 @@ REFLECT_STRUCT(TextDocumentContentChangeEvent, range, rangeLength, text);
 REFLECT_STRUCT(TextDocumentDidChangeParam, textDocument, contentChanges);
 REFLECT_STRUCT(TextDocumentPositionParam, textDocument, position);
 REFLECT_STRUCT(RenameParam, textDocument, position, newName);
+REFLECT_STRUCT(CallsParam, item);
 
 // completion
 REFLECT_UNDERLYING(CompletionTriggerKind);
@@ -162,6 +163,8 @@ MessageHandler::MessageHandler() {
   bind("$ccls/navigate", &MessageHandler::ccls_navigate);
   bind("$ccls/reload", &MessageHandler::ccls_reload);
   bind("$ccls/vars", &MessageHandler::ccls_vars);
+  bind("callHierarchy/incomingCalls", &MessageHandler::callHierarchy_incomingCalls);
+  bind("callHierarchy/outgoingCalls", &MessageHandler::callHierarchy_outgoingCalls);
   bind("exit", &MessageHandler::exit);
   bind("initialize", &MessageHandler::initialize);
   bind("initialized", &MessageHandler::initialized);
@@ -183,6 +186,7 @@ MessageHandler::MessageHandler() {
   bind("textDocument/hover", &MessageHandler::textDocument_hover);
   bind("textDocument/implementation", &MessageHandler::textDocument_implementation);
   bind("textDocument/onTypeFormatting", &MessageHandler::textDocument_onTypeFormatting);
+  bind("textDocument/prepareCallHierarchy", &MessageHandler::textDocument_prepareCallHierarchy);
   bind("textDocument/rangeFormatting", &MessageHandler::textDocument_rangeFormatting);
   bind("textDocument/references", &MessageHandler::textDocument_references);
   bind("textDocument/rename", &MessageHandler::textDocument_rename);
diff --git a/src/message_handler.hh b/src/message_handler.hh
index 7718e346..a5833fee 100644
--- a/src/message_handler.hh
+++ b/src/message_handler.hh
@@ -58,6 +58,22 @@ struct WorkspaceEdit {
 };
 REFLECT_STRUCT(WorkspaceEdit, documentChanges);
 
+struct CallHierarchyItem {
+  std::string name;
+  SymbolKind kind;
+  std::string detail;
+  DocumentUri uri;
+  lsRange range;
+  lsRange selectionRange;
+  std::string data;
+};
+REFLECT_STRUCT(CallHierarchyItem, name, kind, detail, uri, range,
+               selectionRange, data);
+
+struct CallsParam {
+  CallHierarchyItem item;
+};
+
 // completion
 enum class CompletionTriggerKind {
   Invoked = 1,
@@ -259,6 +275,8 @@ private:
   void ccls_navigate(JsonReader &, ReplyOnce &);
   void ccls_reload(JsonReader &);
   void ccls_vars(JsonReader &, ReplyOnce &);
+  void callHierarchy_incomingCalls(CallsParam &param, ReplyOnce &);
+  void callHierarchy_outgoingCalls(CallsParam &param, ReplyOnce &);
   void exit(EmptyParam &);
   void initialize(JsonReader &, ReplyOnce &);
   void initialized(EmptyParam &);
@@ -281,6 +299,8 @@ private:
   void textDocument_implementation(TextDocumentPositionParam &, ReplyOnce &);
   void textDocument_onTypeFormatting(DocumentOnTypeFormattingParam &,
                                      ReplyOnce &);
+  void textDocument_prepareCallHierarchy(TextDocumentPositionParam &,
+                                         ReplyOnce &);
   void textDocument_rangeFormatting(DocumentRangeFormattingParam &,
                                     ReplyOnce &);
   void textDocument_references(JsonReader &, ReplyOnce &);
diff --git a/src/messages/ccls_call.cc b/src/messages/ccls_call.cc
index 5fd3021e..3cb2850e 100644
--- a/src/messages/ccls_call.cc
+++ b/src/messages/ccls_call.cc
@@ -6,6 +6,7 @@
 #include "pipeline.hh"
 #include "query.hh"
 
+#include <map>
 #include <unordered_set>
 
 namespace ccls {
@@ -60,6 +61,18 @@ struct Out_cclsCall {
 REFLECT_STRUCT(Out_cclsCall, id, name, location, callType, numChildren,
                children);
 
+struct Out_incomingCall {
+  CallHierarchyItem from;
+  std::vector<lsRange> fromRanges;
+};
+REFLECT_STRUCT(Out_incomingCall, from, fromRanges);
+
+struct Out_outgoingCall {
+  CallHierarchyItem to;
+  std::vector<lsRange> fromRanges;
+};
+REFLECT_STRUCT(Out_outgoingCall, to, fromRanges);
+
 bool expand(MessageHandler *m, Out_cclsCall *entry, bool callee,
             CallType call_type, bool qualified, int levels) {
   const QueryFunc &func = m->db->getFunc(entry->usr);
@@ -205,4 +218,122 @@ void MessageHandler::ccls_call(JsonReader &reader, ReplyOnce &reply) {
   else
     reply(flattenHierarchy(result));
 }
+
+void MessageHandler::textDocument_prepareCallHierarchy(
+    TextDocumentPositionParam &param, ReplyOnce &reply) {
+  std::string path = param.textDocument.uri.getPath();
+  auto [file, wf] = findOrFail(path, reply);
+  if (!file)
+    return;
+
+  std::vector<CallHierarchyItem> result;
+  for (SymbolRef sym : findSymbolsAtLocation(wf, file, param.position)) {
+    if (sym.kind != Kind::Func)
+      continue;
+    const auto *def = db->getFunc(sym.usr).anyDef();
+    if (!def)
+      continue;
+    auto r = getLsRange(wf, sym.range);
+    if (!r)
+      continue;
+    CallHierarchyItem &item = result.emplace_back();
+    item.name = def->name(false);
+    item.kind = def->kind;
+    item.detail = def->name(true);
+    item.uri = DocumentUri::fromPath(path);
+    item.range = item.selectionRange = *r;
+    item.data = std::to_string(sym.usr);
+  }
+  reply(result);
+}
+
+static lsRange toLsRange(Range r) {
+  return {{r.start.line, r.start.column}, {r.end.line, r.end.column}};
+}
+
+static void
+add(std::map<SymbolIdx, std::pair<int, std::vector<lsRange>>> &sym2ranges,
+    SymbolRef sym, int file_id) {
+  auto [it, inserted] = sym2ranges.try_emplace(SymbolIdx{sym.usr, sym.kind});
+  if (inserted)
+    it->second.first = file_id;
+  if (it->second.first == file_id)
+    it->second.second.push_back(toLsRange(sym.range));
+}
+
+template <typename Out>
+static std::vector<Out> toCallResult(
+    DB *db,
+    const std::map<SymbolIdx, std::pair<int, std::vector<lsRange>>> &sym2ranges) {
+  std::vector<Out> result;
+  for (auto &[sym, ranges] : sym2ranges) {
+    CallHierarchyItem item;
+    item.uri = getLsDocumentUri(db, ranges.first);
+    auto r = ranges.second[0];
+    item.range = {{uint16_t(r.start.line), int16_t(r.start.character)},
+                  {uint16_t(r.end.line), int16_t(r.end.character)}};
+    item.selectionRange = item.range;
+    switch (sym.kind) {
+    default:
+      continue;
+    case Kind::Func: {
+      auto idx = db->func_usr[sym.usr];
+      const QueryFunc &func = db->funcs[idx];
+      const QueryFunc::Def *def = func.anyDef();
+      if (!def)
+        continue;
+      item.name = def->name(false);
+      item.kind = def->kind;
+      item.detail = def->name(true);
+      item.data = std::to_string(sym.usr);
+    }
+    }
+
+    result.push_back({std::move(item), std::move(ranges.second)});
+  }
+  return result;
+}
+
+void MessageHandler::callHierarchy_incomingCalls(CallsParam &param,
+                                                 ReplyOnce &reply) {
+  Usr usr;
+  try {
+    usr = std::stoull(param.item.data);
+  } catch (...) {
+    return;
+  }
+  const QueryFunc &func = db->getFunc(usr);
+  std::map<SymbolIdx, std::pair<int, std::vector<lsRange>>> sym2ranges;
+  for (Use use : func.uses) {
+    const QueryFile &file = db->files[use.file_id];
+    Maybe<ExtentRef> best;
+    for (auto [sym, refcnt] : file.symbol2refcnt)
+      if (refcnt > 0 && sym.extent.valid() && sym.kind == Kind::Func &&
+          sym.extent.start <= use.range.start &&
+          use.range.end <= sym.extent.end &&
+          (!best || best->extent.start < sym.extent.start))
+        best = sym;
+    if (best)
+      add(sym2ranges, *best, use.file_id);
+  }
+  reply(toCallResult<Out_incomingCall>(db, sym2ranges));
+}
+
+void MessageHandler::callHierarchy_outgoingCalls(CallsParam &param,
+                                                 ReplyOnce &reply) {
+  Usr usr;
+  try {
+    usr = std::stoull(param.item.data);
+  } catch (...) {
+    return;
+  }
+  const QueryFunc &func = db->getFunc(usr);
+  std::map<SymbolIdx, std::pair<int, std::vector<lsRange>>> sym2ranges;
+  if (const auto *def = func.anyDef())
+    for (SymbolRef sym : def->callees)
+      if (sym.kind == Kind::Func) {
+        add(sym2ranges, sym, def->file_id);
+      }
+  reply(toCallResult<Out_outgoingCall>(db, sym2ranges));
+}
 } // namespace ccls
diff --git a/src/messages/initialize.cc b/src/messages/initialize.cc
index ea07006d..e7a71d54 100644
--- a/src/messages/initialize.cc
+++ b/src/messages/initialize.cc
@@ -88,6 +88,7 @@ struct ServerCap {
   struct ExecuteCommandOptions {
     std::vector<const char *> commands = {ccls_xref};
   } executeCommandProvider;
+  bool callHierarchyProvider = true;
   Config::ServerCap::Workspace workspace;
 };
 REFLECT_STRUCT(ServerCap::CodeActionOptions, codeActionKinds);
@@ -109,7 +110,7 @@ REFLECT_STRUCT(ServerCap, textDocumentSync, hoverProvider, completionProvider,
                documentRangeFormattingProvider,
                documentOnTypeFormattingProvider, renameProvider,
                documentLinkProvider, foldingRangeProvider,
-               executeCommandProvider, workspace);
+               executeCommandProvider, callHierarchyProvider, workspace);
 
 struct DynamicReg {
   bool dynamicRegistration = false;