diff --git a/mp_api/client/core/client.py b/mp_api/client/core/client.py
index 635648ed..07c6c4be 100644
--- a/mp_api/client/core/client.py
+++ b/mp_api/client/core/client.py
@@ -675,7 +675,7 @@ def _submit_request_and_process(
             Tuple with data and total number of docs in matching the query in the database.
         """
         try:
-            response = self.session.get(url=url, verify=verify, params=params, timeout=timeout)
+            response = self.session.get(url=url, verify=verify, params=params, timeout=timeout, headers=self.headers)
         except requests.exceptions.ConnectTimeout:
             raise MPRestError(f"REST query timed out on URL {url}. Try again with a smaller request.")
 
diff --git a/mp_api/client/mprester.py b/mp_api/client/mprester.py
index a8427ff0..8d70e827 100644
--- a/mp_api/client/mprester.py
+++ b/mp_api/client/mprester.py
@@ -17,7 +17,7 @@
 from pymatgen.entries.computed_entries import ComputedEntry, ComputedStructureEntry
 from pymatgen.io.vasp import Chgcar
 from pymatgen.symmetry.analyzer import SpacegroupAnalyzer
-from requests import get
+from requests import get, Session
 from typing import Literal
 
 from mp_api.client.core import BaseRester, MPRestError
@@ -85,6 +85,7 @@ def __init__(
         include_user_agent=True,
         monty_decode: bool = True,
         use_document_model: bool = True,
+        session: Session = None,
         headers: dict = None,
     ):
         """
@@ -116,6 +117,7 @@ def __init__(
             use_document_model: If False, skip the creating the document model and return data
                 as a dictionary. This can be simpler to work with but bypasses data validation
                 and will not give auto-complete for available fields.
+            session (Session): Session object to use. By default (None), the client will create one.
             headers (dict): Custom headers for localhost connections.
         """
 
@@ -129,7 +131,7 @@ def __init__(
         self.api_key = api_key
         self.endpoint = endpoint
         self.headers = headers or {}
-        self.session = BaseRester._create_session(
+        self.session = session or BaseRester._create_session(
             api_key=api_key, include_user_agent=include_user_agent, headers=self.headers
         )
         self.use_document_model = use_document_model
@@ -138,7 +140,7 @@ def __init__(
         try:
             from mpcontribs.client import Client
 
-            self.contribs = Client(api_key, headers=self.headers)
+            self.contribs = Client(api_key, headers=self.headers, sesson=self.session)
         except ImportError:
             self.contribs = None
             warnings.warn(
@@ -167,6 +169,7 @@ def __init__(
                 session=self.session,
                 monty_decode=monty_decode,
                 use_document_model=use_document_model,
+                headers=self.headers
             )  # type: BaseRester
 
             self._all_resters.append(rester)