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
@@ -21,6 +21,7 @@
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclBase.h"
 #include "clang/AST/DeclTemplate.h"
+#include "clang/AST/Expr.h"
 #include "clang/AST/PrettyPrinter.h"
 #include "clang/AST/Type.h"
 #include "clang/Index/IndexSymbol.h"
@@ -445,9 +446,13 @@
         // Look for a close enclosing expression to show the value of.
         if (!HI->Value)
           HI->Value = printExprValue(N, AST.getASTContext());
+      } else if (const Expr *E = N->ASTNode.get<Expr>()) {
+        // For expressions we currently print the type and the value, if they
+        // are evaluatable.
+        HI = getHoverContents(E->getType(), AST.getASTContext(), Index);
+        HI->Value = printExprValue(E, AST.getASTContext());
       }
       // FIXME: support hovers for other nodes?
-      //  - certain expressions (sizeof etc)
       //  - built-in types
       //  - literals (esp user-defined)
     }
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
@@ -1512,6 +1512,30 @@
             HI.Name = "b";
             HI.Type = "int";
           }},
+      {
+          R"cpp(// sizeof expr
+          void foo() {
+            (void)[[size^of]](char);
+          })cpp",
+          [](HoverInfo &HI) {
+            HI.Name = "unsigned long";
+            HI.Value = "1";
+          }},
+      {
+          R"cpp(// alignof expr
+          void foo() {
+            (void)[[align^of]](char);
+          })cpp",
+          [](HoverInfo &HI) {
+            HI.Name = "unsigned long";
+            HI.Value = "1";
+          }},
+      {
+          R"cpp(// non-evaluatable expr
+          template <typename T> void foo() {
+            (void)[[size^of]](T);
+          })cpp",
+          [](HoverInfo &HI) { HI.Name = "unsigned long"; }},
   };
 
   // Create a tiny index, so tests above can verify documentation is fetched.