diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 8521d3b07b..4637847987 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   Ensure concurrent invocations of the connection reaper cannot allocate the
+    same connection to two threads.
+
+    Fixes #25585.
+
+    *Matthew Draper*
+
 *   Inspecting an object with an associated array of over 10 elements no longer
     truncates the array, preventing `inspect` from looping infinitely in some
     cases.
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
index c341773be1..51bbc02b0c 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
@@ -561,6 +561,8 @@ module ActiveRecord
 
         stale_connections.each do |conn|
           synchronize do
+            next unless conn.in_use? && !conn.owner.alive?
+
             if conn.active?
               conn.reset!
               checkin conn