diff --git a/httpie/output/writer.py b/httpie/output/writer.py
index 4a2949bce2..41de5738ed 100644
--- a/httpie/output/writer.py
+++ b/httpie/output/writer.py
@@ -46,7 +46,7 @@ def write_message(
         'flush': env.stdout_isatty or processing_options.stream
     }
     try:
-        if env.is_windows and 'colors' in processing_options.get_prettify(env):
+        if env.is_windows and env.stdout_isatty and 'colors' in processing_options.get_prettify(env):
             write_stream_with_colors_win(**write_stream_kwargs)
         else:
             write_stream(**write_stream_kwargs)
diff --git a/tests/test_windows.py b/tests/test_windows.py
index 80d392ae8f..42c7fc9e63 100644
--- a/tests/test_windows.py
+++ b/tests/test_windows.py
@@ -1,3 +1,5 @@
+from unittest import mock
+
 import pytest
 from httpie.context import Environment
 
@@ -23,3 +25,18 @@ def test_output_file_pretty_not_allowed_on_windows(self, tmp_path, httpbin):
                  '--pretty=all', 'GET', httpbin + '/get',
                  env=env, tolerate_error_exit_status=True)
         assert 'Only terminal output can be colorized on Windows' in r.stderr
+
+    def test_windows_piped_pretty_uses_raw_stream(self, httpbin):
+        """When stdout is piped on Windows, write_stream() should be used
+        instead of write_stream_with_colors_win() so ANSI codes pass
+        through to pagers like `less -r`. Regression test for #799."""
+        env = MockEnvironment(
+            is_windows=True,
+            stdout_isatty=False,
+            colors=256,
+        )
+        with mock.patch('httpie.output.writer.write_stream') as write_stream, \
+             mock.patch('httpie.output.writer.write_stream_with_colors_win') as write_colors_win:
+            http('--pretty=all', 'GET', httpbin + '/get', env=env)
+            write_stream.assert_called()
+            write_colors_win.assert_not_called()