diff --git a/clang-tools-extra/clangd/Hover.cpp b/clang-tools-extra/clangd/Hover.cpp
--- a/clang-tools-extra/clangd/Hover.cpp
+++ b/clang-tools-extra/clangd/Hover.cpp
@@ -265,12 +265,17 @@
   } else if (llvm::isa<CXXDestructorDecl>(FD)) {
     HI.ReturnType = "void";
   } else {
-    HI.ReturnType = FD->getReturnType().getAsString(Policy);
-
-    QualType FunctionType = FD->getType();
+    QualType QT = FD->getReturnType();
+    // TypePrinter doesn't resolve decltypes, so resolve them here. We are going
+    // to include spelling "decltype(X)" in `HoverInfo::Definition` anyway.
+    while (auto *DT = QT->getAs<DecltypeType>())
+      QT = DT->getUnderlyingType();
+    HI.ReturnType = QT.getAsString(Policy);
+
+    QT = FD->getType();
     if (const VarDecl *VD = llvm::dyn_cast<VarDecl>(D)) // Lambdas
-      FunctionType = VD->getType().getDesugaredType(D->getASTContext());
-    HI.Type = FunctionType.getAsString(Policy);
+      QT = VD->getType().getDesugaredType(D->getASTContext());
+    HI.Type = QT.getAsString(Policy);
   }
   // FIXME: handle variadics.
 }
@@ -352,8 +357,14 @@
   // Fill in types and params.
   if (const FunctionDecl *FD = getUnderlyingFunction(D))
     fillFunctionTypeAndParams(HI, D, FD, Policy);
-  else if (const auto *VD = dyn_cast<ValueDecl>(D))
-    HI.Type = VD->getType().getAsString(Policy);
+  else if (const auto *VD = dyn_cast<ValueDecl>(D)) {
+    QualType QT = VD->getType();
+    // TypePrinter doesn't resolve decltypes, so resolve them here. We are going
+    // to include spelling "decltype(X)" in `HoverInfo::Definition` anyway.
+    while (auto *DT = QT->getAs<DecltypeType>())
+      QT = DT->getUnderlyingType();
+    HI.Type = QT.getAsString(Policy);
+  }
 
   // Fill in value with evaluated initializer if possible.
   if (const auto *Var = dyn_cast<VarDecl>(D)) {
diff --git a/clang-tools-extra/clangd/unittests/HoverTests.cpp b/clang-tools-extra/clangd/unittests/HoverTests.cpp
--- a/clang-tools-extra/clangd/unittests/HoverTests.cpp
+++ b/clang-tools-extra/clangd/unittests/HoverTests.cpp
@@ -1534,6 +1534,53 @@
             HI.Type = "unsigned long";
             HI.Value = "1";
           }},
+      {
+          R"cpp(// type with decltype
+          int a;
+          decltype(a) [[b^]] = a;)cpp",
+          [](HoverInfo &HI) {
+            HI.Definition = "decltype(a) b = a";
+            HI.Kind = index::SymbolKind::Variable;
+            HI.NamespaceScope = "";
+            HI.Name = "b";
+            HI.Type = "int";
+          }},
+      {
+          R"cpp(// type with decltype
+          int a;
+          decltype(a) c;
+          decltype(c) [[b^]] = a;)cpp",
+          [](HoverInfo &HI) {
+            HI.Definition = "decltype(c) b = a";
+            HI.Kind = index::SymbolKind::Variable;
+            HI.NamespaceScope = "";
+            HI.Name = "b";
+            HI.Type = "int";
+          }},
+      {
+          R"cpp(// type with decltype
+          int a;
+          const decltype(a) [[b^]] = a;)cpp",
+          [](HoverInfo &HI) {
+            HI.Definition = "const decltype(a) b = a";
+            HI.Kind = index::SymbolKind::Variable;
+            HI.NamespaceScope = "";
+            HI.Name = "b";
+            HI.Type = "int";
+          }},
+      {
+          R"cpp(// type with decltype
+          int a;
+          auto [[f^oo]]() -> decltype(a) { return 0; })cpp",
+          [](HoverInfo &HI) {
+            HI.Definition = "auto foo() -> decltype(a)";
+            HI.Kind = index::SymbolKind::Function;
+            HI.NamespaceScope = "";
+            HI.Name = "foo";
+            HI.Type = "auto () -> decltype(a)";
+            HI.ReturnType = "int";
+            HI.Parameters.emplace();
+          }},
   };
 
   // Create a tiny index, so tests above can verify documentation is fetched.