diff --git a/docs/changelog.md b/docs/changelog.md
index d752f1fc8a..9c624ef563 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -33,6 +33,9 @@ Internal:
 
 Bug fixes:
 
+- Fixed test builds with installed Eigen 5 by improving `Eigen3` CMake package detection.
+  [#6036](https://github.com/pybind/pybind11/pull/6036)
+
 - Fixed move semantics of `scoped_ostream_redirect` to preserve buffered output and avoid crashes when moved redirects restore stream buffers.
   [#6033](https://github.com/pybind/pybind11/pull/6033)
 
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index d5d597cdff..fc08a9056f 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -300,10 +300,17 @@ if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
 
   else()
     find_package(Eigen3 3.2.7 QUIET CONFIG)
+    if(NOT Eigen3_FOUND)
+      find_package(Eigen3 5 QUIET CONFIG)
+    endif()
+    set(EIGEN3_FOUND ${Eigen3_FOUND})
+    set(EIGEN3_VERSION ${Eigen3_VERSION})
 
     if(NOT EIGEN3_FOUND)
       # Couldn't load via target, so fall back to allowing module mode finding, which will pick up
       # tools/FindEigen3.cmake
+      # This MODULE-mode fallback is for older Eigen 3 setups; Eigen 5 is expected to be found
+      # via the CONFIG-mode probes above.
       find_package(Eigen3 3.2.7 QUIET)
     endif()
   endif()