diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7eb17cd1..1f9539c5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+- `OpenapiFirst::FileLoader` will now cache the contents of files that have been loaded. This cache
+  is keyed on the file's path. If you need to reload your OpenAPI definition for tests or server hot
+  reloading, you can run `OpenapiFirst::FileLoader.clear_cache!`.
+
 ## 3.2.1
 
 - Don't raise `UnknownQueryParameterError` if request is ignored in tests. Fixes [#441](https://github.com/ahx/openapi_first/issues/441).
diff --git a/lib/openapi_first/file_loader.rb b/lib/openapi_first/file_loader.rb
index 45082412..8dc4dcd1 100644
--- a/lib/openapi_first/file_loader.rb
+++ b/lib/openapi_first/file_loader.rb
@@ -6,17 +6,32 @@
 module OpenapiFirst
   # @!visibility private
   module FileLoader
+    @cache = {}
+    @mutex = Mutex.new
+
     module_function
 
     def load(file_path)
-      raise FileNotFoundError, "File not found #{file_path.inspect}" unless File.exist?(file_path)
+      @cache[file_path] || @mutex.synchronize do
+        @cache[file_path] ||= begin
+          raise FileNotFoundError, "File not found #{file_path.inspect}" unless File.exist?(file_path)
+
+          body = File.read(file_path)
+          extname = File.extname(file_path)
 
-      body = File.read(file_path)
-      extname = File.extname(file_path)
-      return ::JSON.parse(body) if extname == '.json'
-      return YAML.unsafe_load(body) if ['.yaml', '.yml'].include?(extname)
+          if extname == '.json'
+            ::JSON.parse(body)
+          elsif ['.yaml', '.yml'].include?(extname)
+            YAML.unsafe_load(body)
+          else
+            body
+          end
+        end
+      end
+    end
 
-      body
+    def clear_cache!
+      @mutex.synchronize { @cache.clear }
     end
   end
 end