diff --git a/aider/main.py b/aider/main.py
index 15a7c6d31..925d8a444 100644
--- a/aider/main.py
+++ b/aider/main.py
@@ -1,4 +1,6 @@
+import os
 import sys
+import git
 import configargparse
 from dotenv import load_dotenv
 from aider.coder import Coder
@@ -11,7 +13,24 @@ def main(args=None, input=None, output=None):
 
     load_dotenv()
     env_prefix = "AIDER_"
-    parser = configargparse.ArgumentParser(description="aider - chat with GPT about your code")
+    def get_git_root():
+    try:
+        repo = git.Repo(search_parent_directories=True)
+        return repo.working_tree_dir
+    except git.InvalidGitRepositoryError:
+        return None
+
+git_root = get_git_root()
+if git_root:
+    default_config_file = os.path.join(git_root, ".aider.conf.yml")
+else:
+    default_config_file = os.path.expanduser("~/.aider.conf.yml")
+
+parser = configargparse.ArgumentParser(
+    description="aider - chat with GPT about your code",
+    add_config_file_help=True,
+    default_config_files=[default_config_file],
+)
     parser.add_argument(
         "files",
         metavar="FILE",