diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index dd060313..d9f3fdff 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -55,6 +55,7 @@ Changed
     - Update REST API versioning (#1936)
     - Update REST API views for OpenAPI compatibility (#1951)
     - Return ``503`` in ``ZoneSubmitMoveAPIView`` if project is locked (#1847)
+    - Return ``503`` in ``ZoneCreateAPIView`` if no investigation or iRODS collections (#2036)
 - **Samplesheets**
     - Update REST API versioning (#1936)
     - Update REST API views for OpenAPI compatibility (#1951)
diff --git a/docs_manual/source/sodar_release_notes.rst b/docs_manual/source/sodar_release_notes.rst
index 70a20ea6..c828f121 100644
--- a/docs_manual/source/sodar_release_notes.rst
+++ b/docs_manual/source/sodar_release_notes.rst
@@ -23,6 +23,8 @@ Release for SODAR Core v1.0 upgrade, iRODS v4.3 upgrade and feature updates.
 - Update REST API versioning
 - Update REST API views for OpenAPI support
 - Update lock requiring REST API views to return 503 if project is locked
+- Update landing zone creation REST API view to return 503 if no investigation
+  or iRODS collections
 - Upgrade to Postgres v16
 - Upgrade to python-irodsclient v2.2.0
 - Upgrade to SODAR Core v1.0.2
@@ -73,6 +75,10 @@ REST API Updates
     * ``IrodsDataRequestAcceptAPIView``
         + Return ``503`` if project is locked
 - Landing Zones API
+    * ``ZoneCreateAPIView``
+        + Return ``503`` if Taskflow is not enabled
+        + Return ``503`` if investigation for project is not found
+        + Return ``503`` if project iRODS collections have not been created
     * ``ZoneSubmitMoveAPIView``
         + Return ``503`` if project is locked
 
diff --git a/landingzones/serializers.py b/landingzones/serializers.py
index 3e20e5bf..eff514da 100644
--- a/landingzones/serializers.py
+++ b/landingzones/serializers.py
@@ -1,6 +1,7 @@
 """API view model serializers for the landingzone app"""
 
 from rest_framework import serializers
+from rest_framework.exceptions import APIException
 
 # Projectroles dependency
 from projectroles.plugins import get_backend_api
@@ -10,7 +11,7 @@
 )
 
 # Samplesheets dependency
-from samplesheets.models import Assay
+from samplesheets.models import Investigation, Assay
 
 from landingzones.constants import (
     ZONE_STATUS_OK,
@@ -21,6 +22,10 @@
 from landingzones.utils import get_zone_title
 
 
+# Local constants
+ZONE_NO_INV_MSG = 'No investigation found for project'
+
+
 class LandingZoneSerializer(SODARProjectModelSerializer):
     """Serializer for the LandingZone model"""
 
@@ -68,6 +73,15 @@ def get_irods_path(self, obj):
             return irods_backend.get_path(obj)
 
     def validate(self, attrs):
+        # If there is no investigation, we can't have a landing zone
+        investigation = Investigation.objects.filter(
+            project=self.context.get('project'), active=True
+        ).first()
+        if not investigation:
+            ex = APIException(ZONE_NO_INV_MSG)
+            ex.status_code = 503
+            raise ex
+        # Else continue validating the input
         try:
             if 'assay' in attrs:
                 assay = Assay.objects.get(
diff --git a/landingzones/tests/test_views_api_taskflow.py b/landingzones/tests/test_views_api_taskflow.py
index 180a032c..6b3eaaee 100644
--- a/landingzones/tests/test_views_api_taskflow.py
+++ b/landingzones/tests/test_views_api_taskflow.py
@@ -30,6 +30,7 @@
     ZONE_STATUS_FAILED,
 )
 from landingzones.models import LandingZone
+from landingzones.serializers import ZONE_NO_INV_MSG
 from landingzones.tests.test_models import LandingZoneMixin
 from landingzones.tests.test_views_taskflow import (
     LandingZoneTaskflowMixin,
@@ -44,6 +45,7 @@
 from landingzones.views_api import (
     LANDINGZONES_API_MEDIA_TYPE,
     LANDINGZONES_API_DEFAULT_VERSION,
+    ZONE_NO_COLLS_MSG,
 )
 
 
@@ -290,7 +292,8 @@ def test_post_no_investigation(self):
             'config_data': {},
         }
         response = self.request_knox(self.url, method='POST', data=request_data)
-        self.assertEqual(response.status_code, 400)
+        self.assertEqual(response.status_code, 503)
+        self.assertEqual(ZONE_NO_INV_MSG, response.data['detail'])
         self.assertEqual(LandingZone.objects.count(), 0)
 
     def test_post_no_irods_collections(self):
@@ -306,7 +309,8 @@ def test_post_no_irods_collections(self):
             'config_data': {},
         }
         response = self.request_knox(self.url, method='POST', data=request_data)
-        self.assertEqual(response.status_code, 400)
+        self.assertEqual(response.status_code, 503)
+        self.assertIn(ZONE_NO_COLLS_MSG, response.data['detail'])
         self.assertEqual(LandingZone.objects.count(), 0)
 
 
diff --git a/landingzones/views_api.py b/landingzones/views_api.py
index 4464469f..c9ecd05c 100644
--- a/landingzones/views_api.py
+++ b/landingzones/views_api.py
@@ -5,6 +5,7 @@
 
 from django.urls import reverse
 
+from rest_framework import status
 from rest_framework.exceptions import APIException, NotFound
 from rest_framework.generics import (
     ListAPIView,
@@ -14,7 +15,6 @@
 )
 from rest_framework.renderers import JSONRenderer
 from rest_framework.response import Response
-from rest_framework import status
 from rest_framework.serializers import ValidationError
 from rest_framework.schemas.openapi import AutoSchema
 from rest_framework.versioning import AcceptHeaderVersioning
@@ -51,6 +51,8 @@
 LANDINGZONES_API_ALLOWED_VERSIONS = ['1.0']
 LANDINGZONES_API_DEFAULT_VERSION = '1.0'
 
+ZONE_NO_COLLS_MSG = 'iRODS collections not created for project'
+
 
 # Mixins and Base Views --------------------------------------------------------
 
@@ -214,6 +216,9 @@ class ZoneCreateAPIView(
     """
     Create a landing zone.
 
+    Returns ``503`` if an investigation for the project is not found or project
+    iRODS collections have not been created.
+
     **URL:** ``/landingzones/api/create/{Project.sodar_uuid}``
 
     **Methods:** ``POST``
@@ -237,29 +242,29 @@ class ZoneCreateAPIView(
     permission_required = 'landingzones.create_zone'
     serializer_class = LandingZoneSerializer
 
+    @classmethod
+    def _raise_503(cls, msg):
+        ex = APIException(msg)
+        ex.status_code = 503
+        raise ex
+
     def perform_create(self, serializer):
         """
         Override perform_create() to add timeline event and initiate taskflow.
         """
-        ex_msg = 'Creating landing zone failed: '
+        ex_prefix = 'Creating landing zone failed: '
         # Check taskflow status
         if not get_backend_api('taskflow'):
-            raise APIException('{}Taskflow not enabled'.format(ex_msg))
+            self._raise_503('{}Taskflow not enabled'.format(ex_prefix))
 
         # Ensure project has investigation with iRODS collections created
         project = self.get_project()
         investigation = Investigation.objects.filter(
             active=True, project=project
         ).first()
-
-        if not investigation:
-            raise ValidationError(
-                '{}No investigation found for project'.format(ex_msg)
-            )
+        # NOTE: Lack of investigation is already caught in serializer
         if not investigation.irods_status:
-            raise ValidationError(
-                '{}iRODS collections not created for project'.format(ex_msg)
-            )
+            self._raise_503('{}{}'.format(ex_prefix, ZONE_NO_COLLS_MSG))
 
         # If all is OK, go forward with object creation and taskflow submission
         create_colls = serializer.validated_data.pop('create_colls')
@@ -273,7 +278,7 @@ def perform_create(self, serializer):
                 request=self.request,
             )
         except Exception as ex:
-            raise APIException('{}{}'.format(ex_msg, ex))
+            raise APIException('{}{}'.format(ex_prefix, ex))
 
 
 class ZoneUpdateAPIView(