diff --git a/docs/source/python/filesystems.rst b/docs/source/python/filesystems.rst
index 40656f6b76f43..3fc10dc7718d3 100644
--- a/docs/source/python/filesystems.rst
+++ b/docs/source/python/filesystems.rst
@@ -153,8 +153,9 @@ PyArrow implements natively a S3 filesystem for S3 compatible storage.
 The :class:`S3FileSystem` constructor has several options to configure the S3
 connection (e.g. credentials, the region, an endpoint override, etc). In
 addition, the constructor will also inspect configured S3 credentials as
-supported by AWS (for example the ``AWS_ACCESS_KEY_ID`` and
-``AWS_SECRET_ACCESS_KEY`` environment variables).
+supported by AWS (such as the ``AWS_ACCESS_KEY_ID`` and
+``AWS_SECRET_ACCESS_KEY`` environment variables, AWS configuration files,
+and EC2 Instance Metadata Service for EC2 nodes).
 
 
 Example how you can read contents from a S3 bucket::
diff --git a/python/pyarrow/_s3fs.pyx b/python/pyarrow/_s3fs.pyx
index e76c7b9ffa730..51c248d147828 100644
--- a/python/pyarrow/_s3fs.pyx
+++ b/python/pyarrow/_s3fs.pyx
@@ -140,14 +140,20 @@ cdef class S3FileSystem(FileSystem):
     """
     S3-backed FileSystem implementation
 
-    If neither access_key nor secret_key are provided, and role_arn is also not
-    provided, then attempts to initialize from AWS environment variables,
-    otherwise both access_key and secret_key must be provided.
+    AWS access_key and secret_key can be provided explicitly.
 
     If role_arn is provided instead of access_key and secret_key, temporary
     credentials will be fetched by issuing a request to STS to assume the
     specified role.
 
+    If neither access_key nor secret_key are provided, and role_arn is also not
+    provided, then attempts to establish the credentials automatically.
+    S3FileSystem will try the following methods, in order:
+
+    * ``AWS_ACCESS_KEY_ID``, ``AWS_SECRET_ACCESS_KEY``, and ``AWS_SESSION_TOKEN`` environment variables
+    * configuration files such as ``~/.aws/credentials`` and ``~/.aws/config``
+    * for nodes on Amazon EC2, the EC2 Instance Metadata Service
+
     Note: S3 buckets are special and the operations available on them may be
     limited or more expensive than desired.