diff --git a/customerio/client_base.py b/customerio/client_base.py
index 1096336..6e95bad 100644
--- a/customerio/client_base.py
+++ b/customerio/client_base.py
@@ -2,7 +2,6 @@
 Implements the base client that is used by other classes to make requests.
 """
 
-import logging
 import math
 from datetime import datetime, timezone
 
@@ -28,7 +27,7 @@ def __init__(self, retries=3, timeout=10, backoff_factor=0.02, use_connection_po
     @property
     def http(self):
         if self._current_session is None:
-            self._current_session = self._get_session()
+            self._current_session = self._build_session()
 
         return self._current_session
 
@@ -36,12 +35,21 @@ def send_request(self, method, url, data):
         """Dispatches the request and returns a response."""
 
         try:
-            response = self.http.request(
-                method,
-                url=url,
-                json=self._sanitize(data),
-                timeout=self.timeout,
-            )
+            if self.use_connection_pooling:
+                response = self.http.request(
+                    method,
+                    url=url,
+                    json=self._sanitize(data),
+                    timeout=self.timeout,
+                )
+            else:
+                with self._build_session() as http:
+                    response = http.request(
+                        method,
+                        url=url,
+                        json=self._sanitize(data),
+                        timeout=self.timeout,
+                    )
 
             result_status = response.status_code
             if result_status != 200:
@@ -57,9 +65,6 @@ def send_request(self, method, url, data):
             """
             raise CustomerIOException(message) from e
 
-        finally:
-            self._close()
-
     def _sanitize(self, data):
         return {key: self._sanitize_value(value) for key, value in data.items()}
 
@@ -84,18 +89,6 @@ def _stringify_list(self, customer_ids):
                 raise CustomerIOException(f"customer_ids cannot be {type(v)}")
         return customer_string_ids
 
-    def _get_session(self):
-        if self.use_connection_pooling:
-            if self._current_session is None:
-                self._current_session = self._build_session()
-
-            logging.debug("Using existing session...")
-            return self._current_session
-
-        logging.debug("Creating new session...")
-        self._current_session = self._build_session()
-        return self._current_session
-
     def _build_session(self):
         session = Session()
         session.headers["User-Agent"] = f"Customer.io Python Client/{ClientVersion}"
@@ -106,8 +99,3 @@ def _build_session(self):
         )
 
         return session
-
-    def _close(self):
-        if not self.use_connection_pooling and self._current_session is not None:
-            self._current_session.close()
-            self._current_session = None
diff --git a/tests/test_client_base.py b/tests/test_client_base.py
new file mode 100644
index 0000000..c6cef74
--- /dev/null
+++ b/tests/test_client_base.py
@@ -0,0 +1,87 @@
+import threading
+import unittest
+
+from customerio.client_base import ClientBase
+
+
+class FakeResponse:
+    status_code = 200
+    text = "ok"
+
+
+class FakeSession:
+    def __init__(self, request_barrier=None):
+        self.closed = False
+        self.request_barrier = request_barrier
+        self.request_count = 0
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args):
+        self.close()
+
+    def request(self, *args, **kwargs):
+        self.request_count += 1
+        if self.request_barrier is not None:
+            self.request_barrier.wait(timeout=5)
+        return FakeResponse()
+
+    def close(self):
+        self.closed = True
+
+
+class TestClientBase(unittest.TestCase):
+    def test_connection_pooling_reuses_session(self):
+        client = ClientBase(use_connection_pooling=True)
+        sessions = []
+
+        def build_session():
+            session = FakeSession()
+            sessions.append(session)
+            return session
+
+        client._build_session = build_session
+
+        self.assertEqual(client.send_request("POST", "https://example.com", {}), "ok")
+        self.assertEqual(client.send_request("POST", "https://example.com", {}), "ok")
+
+        self.assertEqual(len(sessions), 1)
+        self.assertFalse(sessions[0].closed)
+
+    def test_disabled_connection_pooling_isolates_overlapping_requests(self):
+        client = ClientBase(use_connection_pooling=False)
+        request_barrier = threading.Barrier(2)
+        sessions = []
+        responses = []
+        errors = []
+
+        def build_session():
+            session = FakeSession(request_barrier)
+            sessions.append(session)
+            return session
+
+        def send_request():
+            try:
+                responses.append(client.send_request("POST", "https://example.com", {}))
+            except Exception as exc:  # pragma: no cover
+                errors.append(exc)
+
+        client._build_session = build_session
+
+        threads = [threading.Thread(target=send_request) for _ in range(2)]
+        for thread in threads:
+            thread.start()
+        for thread in threads:
+            thread.join()
+
+        self.assertEqual(errors, [])
+        self.assertEqual(sorted(responses), ["ok", "ok"])
+        self.assertEqual(len(sessions), 2)
+        self.assertTrue(all(session.closed for session in sessions))
+        self.assertTrue(all(session.request_count == 1 for session in sessions))
+        self.assertIsNone(client._current_session)
+
+
+if __name__ == "__main__":
+    unittest.main()