diff --git a/gql/transport/aiohttp.py b/gql/transport/aiohttp.py
index bdd53852..7d71f3a9 100644
--- a/gql/transport/aiohttp.py
+++ b/gql/transport/aiohttp.py
@@ -1,3 +1,4 @@
+import json
 from ssl import SSLContext
 from typing import Any, AsyncGenerator, Dict, Optional, Union
 
@@ -8,6 +9,7 @@
 from aiohttp.typedefs import LooseCookies, LooseHeaders
 from graphql import DocumentNode, ExecutionResult, print_ast
 
+from ..utils import extract_files
 from .async_transport import AsyncTransport
 from .exceptions import (
     TransportAlreadyConnected,
@@ -33,7 +35,7 @@ def __init__(
         auth: Optional[BasicAuth] = None,
         ssl: Union[SSLContext, bool, Fingerprint] = False,
         timeout: Optional[int] = None,
-        client_session_args: Dict[str, Any] = {},
+        client_session_args: Optional[Dict[str, Any]] = None,
     ) -> None:
         """Initialize the transport with the given aiohttp parameters.
 
@@ -51,7 +53,6 @@ def __init__(
         self.ssl: Union[SSLContext, bool, Fingerprint] = ssl
         self.timeout: Optional[int] = timeout
         self.client_session_args = client_session_args
-
         self.session: Optional[aiohttp.ClientSession] = None
 
     async def connect(self) -> None:
@@ -76,7 +77,8 @@ async def connect(self) -> None:
                 )
 
             # Adding custom parameters passed from init
-            client_session_args.update(self.client_session_args)
+            if self.client_session_args:
+                client_session_args.update(self.client_session_args)  # type: ignore
 
             self.session = aiohttp.ClientSession(**client_session_args)
 
@@ -93,7 +95,7 @@ async def execute(
         document: DocumentNode,
         variable_values: Optional[Dict[str, str]] = None,
         operation_name: Optional[str] = None,
-        extra_args: Dict[str, Any] = {},
+        extra_args: Dict[str, Any] = None,
     ) -> ExecutionResult:
         """Execute the provided document AST against the configured remote server.
         This uses the aiohttp library to perform a HTTP POST request asynchronously
@@ -103,21 +105,46 @@ async def execute(
         """
 
         query_str = print_ast(document)
+
+        nulled_variable_values = None
+        files = None
+        if variable_values:
+            nulled_variable_values, files = extract_files(variable_values)
+
         payload: Dict[str, Any] = {
             "query": query_str,
         }
 
-        if variable_values:
-            payload["variables"] = variable_values
+        if nulled_variable_values:
+            payload["variables"] = nulled_variable_values
         if operation_name:
             payload["operationName"] = operation_name
 
-        post_args = {
-            "json": payload,
-        }
+        if files:
+            data = aiohttp.FormData()
+
+            # header
+            file_map = {str(i): [path] for i, path in enumerate(files)}
+            # path is nested in a list because the spec allows multiple pointers
+            # to the same file. But we don't use that.
+            file_streams = {
+                str(i): files[path] for i, path in enumerate(files)
+            }  # payload
+
+            data.add_field(
+                "operations", json.dumps(payload), content_type="application/json"
+            )
+            data.add_field("map", json.dumps(file_map), content_type="application/json")
+            data.add_fields(*file_streams.items())
+
+            post_args = {"data": data}
+
+        else:
+            post_args = {"json": payload}  # type: ignore
 
         # Pass post_args to aiohttp post method
-        post_args.update(extra_args)
+        if extra_args:
+            post_args.update(extra_args)  # type: ignore
 
         if self.session is None:
             raise TransportClosed("Transport is not connected")
diff --git a/gql/utils.py b/gql/utils.py
index 8f47d97d..ce0318b0 100644
--- a/gql/utils.py
+++ b/gql/utils.py
@@ -1,5 +1,8 @@
 """Utilities to manipulate several python objects."""
 
+import io
+from typing import Any, Dict, Tuple
+
 
 # From this response in Stackoverflow
 # http://stackoverflow.com/a/19053800/1072990
@@ -8,3 +11,43 @@ def to_camel_case(snake_str):
     # We capitalize the first letter of each component except the first one
     # with the 'title' method and join them together.
     return components[0] + "".join(x.title() if x else "_" for x in components[1:])
+
+
+def is_file_like(value: Any) -> bool:
+    """Check if a value represents a file like object"""
+    return isinstance(value, io.IOBase)
+
+
+def extract_files(variables: Dict) -> Tuple[Dict, Dict]:
+    files = {}
+
+    def recurse_extract(path, obj):
+        """
+        recursively traverse obj, doing a deepcopy, but
+        replacing any file-like objects with nulls and
+        shunting the originals off to the side.
+        """
+        nonlocal files
+        if isinstance(obj, list):
+            nulled_obj = []
+            for key, value in enumerate(obj):
+                value = recurse_extract(f"{path}.{key}", value)
+                nulled_obj.append(value)
+            return nulled_obj
+        elif isinstance(obj, dict):
+            nulled_obj = {}
+            for key, value in obj.items():
+                value = recurse_extract(f"{path}.{key}", value)
+                nulled_obj[key] = value
+            return nulled_obj
+        elif is_file_like(obj):
+            # extract obj from its parent and put it into files instead.
+            files[path] = obj
+            return None
+        else:
+            # base case: pass through unchanged
+            return obj
+
+    nulled_variables = recurse_extract("variables", variables)
+
+    return nulled_variables, files