diff --git a/src/apify_client/_resource_clients/run.py b/src/apify_client/_resource_clients/run.py
index 8c49d02c..aa4956ec 100644
--- a/src/apify_client/_resource_clients/run.py
+++ b/src/apify_client/_resource_clients/run.py
@@ -38,6 +38,14 @@
     from apify_client.types import Timeout
 
 
+def _build_abort_body(*, gracefully: bool | None) -> dict[str, bool]:
+    """Build the JSON body of the abort request, leaving out the options the caller did not set."""
+    body: dict[str, bool] = {}
+    if gracefully is not None:
+        body['gracefully'] = gracefully
+    return body
+
+
 @docs_group('Resource clients')
 class RunClient(ResourceClient):
     """Sub-client for managing a specific Actor run.
@@ -131,7 +139,8 @@ def abort(self, *, gracefully: bool | None = None, timeout: Timeout = 'medium')
         response = self._http_client.call(
             url=self._build_url('abort'),
             method='POST',
-            params=self._build_params(gracefully=gracefully),
+            headers={'content-type': 'application/json'},
+            data=json.dumps(_build_abort_body(gracefully=gracefully)),
             timeout=timeout,
         )
         result = response_to_dict(response)
@@ -678,7 +687,8 @@ async def abort(self, *, gracefully: bool | None = None, timeout: Timeout = 'med
         response = await self._http_client.call(
             url=self._build_url('abort'),
             method='POST',
-            params=self._build_params(gracefully=gracefully),
+            headers={'content-type': 'application/json'},
+            data=json.dumps(_build_abort_body(gracefully=gracefully)),
             timeout=timeout,
         )
         result = response_to_dict(response)
diff --git a/tests/unit/test_run_abort.py b/tests/unit/test_run_abort.py
new file mode 100644
index 00000000..08189b92
--- /dev/null
+++ b/tests/unit/test_run_abort.py
@@ -0,0 +1,102 @@
+from __future__ import annotations
+
+import json
+from typing import TYPE_CHECKING
+
+import pytest
+from werkzeug import Request, Response
+
+from apify_client import ApifyClient, ApifyClientAsync
+
+if TYPE_CHECKING:
+    from pytest_httpserver import HTTPServer
+
+pytestmark = pytest.mark.usefixtures('http_client_classes')
+
+_MOCKED_RUN_ID = 'test_run_id'
+_ABORT_PATH = f'/v2/actor-runs/{_MOCKED_RUN_ID}/abort'
+_RUN_RESPONSE = {
+    'data': {
+        'id': _MOCKED_RUN_ID,
+        'actId': 'test_actor_id',
+        'userId': 'test_user_id',
+        'startedAt': '2024-01-01T00:00:00.000Z',
+        'status': 'ABORTING',
+        'meta': {'origin': 'API'},
+        'stats': {},
+        'options': {'build': 'latest', 'timeoutSecs': 3600, 'memoryMbytes': 1024, 'diskMbytes': 2048},
+        'buildId': 'test_build_id',
+        'defaultKeyValueStoreId': 'test_kvs_id',
+        'defaultDatasetId': 'test_dataset_id',
+        'defaultRequestQueueId': 'test_rq_id',
+        'containerUrl': 'https://example.com',
+    }
+}
+
+
+@pytest.mark.parametrize(
+    ('gracefully', 'expected_body'),
+    [
+        pytest.param(None, {}, id='default'),
+        pytest.param(True, {'gracefully': True}, id='graceful'),
+        pytest.param(False, {'gracefully': False}, id='forced'),
+    ],
+)
+def test_run_abort_sends_gracefully_in_body_sync(
+    httpserver: HTTPServer,
+    *,
+    gracefully: bool | None,
+    expected_body: dict,
+) -> None:
+    """The graceful flag travels in the JSON body and is left out when the caller did not set it."""
+    captured_requests: list[Request] = []
+
+    def capture_request(request: Request) -> Response:
+        captured_requests.append(request)
+        return Response(status=200, response=json.dumps(_RUN_RESPONSE), mimetype='application/json')
+
+    httpserver.expect_request(_ABORT_PATH, method='POST').respond_with_handler(capture_request)
+
+    api_url = httpserver.url_for('/').removesuffix('/')
+    client = ApifyClient(token='test_token', api_url=api_url)
+
+    run = client.run(_MOCKED_RUN_ID).abort(gracefully=gracefully)
+
+    assert run.id == _MOCKED_RUN_ID
+    assert len(captured_requests) == 1
+    assert 'gracefully' not in captured_requests[0].args
+    assert json.loads(captured_requests[0].get_data()) == expected_body
+
+
+@pytest.mark.parametrize(
+    ('gracefully', 'expected_body'),
+    [
+        pytest.param(None, {}, id='default'),
+        pytest.param(True, {'gracefully': True}, id='graceful'),
+        pytest.param(False, {'gracefully': False}, id='forced'),
+    ],
+)
+async def test_run_abort_sends_gracefully_in_body_async(
+    httpserver: HTTPServer,
+    *,
+    gracefully: bool | None,
+    expected_body: dict,
+) -> None:
+    """Async variant of `test_run_abort_sends_gracefully_in_body_sync`."""
+    captured_requests: list[Request] = []
+
+    def capture_request(request: Request) -> Response:
+        captured_requests.append(request)
+        return Response(status=200, response=json.dumps(_RUN_RESPONSE), mimetype='application/json')
+
+    httpserver.expect_request(_ABORT_PATH, method='POST').respond_with_handler(capture_request)
+
+    api_url = httpserver.url_for('/').removesuffix('/')
+    client = ApifyClientAsync(token='test_token', api_url=api_url)
+
+    run = await client.run(_MOCKED_RUN_ID).abort(gracefully=gracefully)
+
+    assert run.id == _MOCKED_RUN_ID
+    assert len(captured_requests) == 1
+    assert 'gracefully' not in captured_requests[0].args
+    assert json.loads(captured_requests[0].get_data()) == expected_body