diff --git a/fixtures/github.py b/fixtures/github.py
index 0563606eca939a..c070ea6cb1826a 100644
--- a/fixtures/github.py
+++ b/fixtures/github.py
@@ -3012,7 +3012,27 @@
       "type": "User",
       "site_admin": false
     },
-    "assignees": [],
+    "assignees": [
+      {
+        "login": "octocat",
+        "id": 1,
+        "avatar_url": "https://avatars.githubusercontent.com/u/1?v=3",
+        "gravatar_id": "",
+        "url": "https://api.github.com/users/octocat",
+        "html_url": "https://github.com/octocat",
+        "followers_url": "https://api.github.com/users/octocat/followers",
+        "following_url": "https://api.github.com/users/octocat/following{/other_user}",
+        "gists_url": "https://api.github.com/users/octocat/gists{/gist_id}",
+        "starred_url": "https://api.github.com/users/octocat/starred{/owner}{/repo}",
+        "subscriptions_url": "https://api.github.com/users/octocat/subscriptions",
+        "organizations_url": "https://api.github.com/users/octocat/orgs",
+        "repos_url": "https://api.github.com/users/octocat/repos",
+        "events_url": "https://api.github.com/users/octocat/events{/privacy}",
+        "received_events_url": "https://api.github.com/users/octocat/received_events",
+        "type": "User",
+        "site_admin": false
+      }
+    ],
     "milestone": null,
     "comments": 0,
     "created_at": "2015-05-05T23:40:28Z",
diff --git a/src/sentry/integrations/github/webhook.py b/src/sentry/integrations/github/webhook.py
index fb62a9d8e8f646..ced99c0efb1272 100644
--- a/src/sentry/integrations/github/webhook.py
+++ b/src/sentry/integrations/github/webhook.py
@@ -547,14 +547,43 @@ def _handle_assignment(
         """
         Handle issue assignment and unassignment events.
 
+        When switching assignees, GitHub sends two webhooks (assigned and unassigned) in
+        non-deterministic order. To avoid race conditions, we sync based on the current
+        state in issue.assignees rather than the delta in the assignee field.
+
         Args:
             integration: The GitHub integration
             event: The webhook event payload
             external_issue_key: The formatted issue key
             action: The action type ('assigned' or 'unassigned')
         """
-        assignee = event.get("assignee", {})
-        assignee_gh_name = assignee.get("login")
+        # Use issue.assignees (current state) instead of assignee (delta) to avoid race conditions
+        issue = event.get("issue", {})
+        assignees = issue.get("assignees", [])
+
+        # If there are no assignees, deassign
+        if not assignees:
+            sync_group_assignee_inbound_by_external_actor(
+                integration=integration,
+                external_user_name="",  # Not used for deassignment
+                external_issue_key=external_issue_key,
+                assign=False,
+            )
+            logger.info(
+                "github.webhook.assignment.synced",
+                extra={
+                    "integration_id": integration.id,
+                    "external_issue_key": external_issue_key,
+                    "assignee_name": None,
+                    "action": "deassigned",
+                },
+            )
+            return
+
+        # GitHub supports multiple assignees, but Sentry currently only supports one
+        # Take the first assignee from the current state
+        first_assignee = assignees[0]
+        assignee_gh_name = first_assignee.get("login")
 
         if not assignee_gh_name:
             logger.warning(
@@ -574,7 +603,7 @@ def _handle_assignment(
             integration=integration,
             external_user_name=assignee_name,
             external_issue_key=external_issue_key,
-            assign=(action == IssueEvenntWebhookActionType.ASSIGNED.value),
+            assign=True,
         )
 
         logger.info(
@@ -584,6 +613,7 @@ def _handle_assignment(
                 "external_issue_key": external_issue_key,
                 "assignee_name": assignee_name,
                 "action": action,
+                "total_assignees": len(assignees),
             },
         )
 
diff --git a/tests/sentry/integrations/github/test_webhooks.py b/tests/sentry/integrations/github/test_webhooks.py
index 46a775c4aac799..ab7d600da8be27 100644
--- a/tests/sentry/integrations/github/test_webhooks.py
+++ b/tests/sentry/integrations/github/test_webhooks.py
@@ -1038,8 +1038,8 @@ def test_assigned_issue(self, mock_record: MagicMock, mock_sync: MagicMock) -> N
             data=ISSUES_ASSIGNED_EVENT_EXAMPLE,
             content_type="application/json",
             HTTP_X_GITHUB_EVENT="issues",
-            HTTP_X_HUB_SIGNATURE="sha1=e19d80f5a6e09e20d126e923464778bb4b601a7e",
-            HTTP_X_HUB_SIGNATURE_256="sha256=e91927e8d8e0db9cb1f5ead889bba2deb24aa2f8925a8eae85ba732424604489",
+            HTTP_X_HUB_SIGNATURE="sha1=75deab06ede0068fe16b5f1f6ee1a9509738e006",
+            HTTP_X_HUB_SIGNATURE_256="sha256=1703af48011c6709662f776163fce1e86772eff189f94e1ebff5ad66a81b711e",
             HTTP_X_GITHUB_DELIVERY=str(uuid4()),
         )
 
@@ -1081,9 +1081,11 @@ def test_unassigned_issue(self, mock_record: MagicMock, mock_sync: MagicMock) ->
 
         rpc_integration = integration_service.get_integration(integration_id=self.integration.id)
 
+        # With the fix, we now use issue.assignees (current state) instead of assignee (delta)
+        # ISSUES_UNASSIGNED_EVENT_EXAMPLE has assignees=[], so we deassign
         mock_sync.assert_called_once_with(
             integration=rpc_integration,
-            external_user_name="@octocat",
+            external_user_name="",
             external_issue_key="baxterthehacker/public-repo#2",
             assign=False,
         )
@@ -1123,8 +1125,8 @@ def test_creates_missing_repo_for_issues(self, mock_metrics: MagicMock) -> None:
             data=ISSUES_ASSIGNED_EVENT_EXAMPLE,
             content_type="application/json",
             HTTP_X_GITHUB_EVENT="issues",
-            HTTP_X_HUB_SIGNATURE="sha1=e19d80f5a6e09e20d126e923464778bb4b601a7e",
-            HTTP_X_HUB_SIGNATURE_256="sha256=e91927e8d8e0db9cb1f5ead889bba2deb24aa2f8925a8eae85ba732424604489",
+            HTTP_X_HUB_SIGNATURE="sha1=75deab06ede0068fe16b5f1f6ee1a9509738e006",
+            HTTP_X_HUB_SIGNATURE_256="sha256=1703af48011c6709662f776163fce1e86772eff189f94e1ebff5ad66a81b711e",
             HTTP_X_GITHUB_DELIVERY=str(uuid4()),
         )