diff --git a/app/Service/Import/Importers/TogglDataImporter.php b/app/Service/Import/Importers/TogglDataImporter.php
index 3fa96789..8bcbb004 100644
--- a/app/Service/Import/Importers/TogglDataImporter.php
+++ b/app/Service/Import/Importers/TogglDataImporter.php
@@ -5,8 +5,11 @@ declare(strict_types=1);
 namespace App\Service\Import\Importers;
 
 use App\Enums\Role;
+use App\Service\TimezoneService;
 use Exception;
 use Illuminate\Support\Carbon;
+use Illuminate\Support\Facades\Log;
+use Illuminate\Support\Str;
 use Override;
 use Spatie\TemporaryDirectory\TemporaryDirectory;
 use ValueError;
@@ -93,11 +96,22 @@ class TogglDataImporter extends DefaultImporter
             }
 
             foreach ($workspaceUsers as $workspaceUser) {
+                $timezone = Str::trim($workspaceUser->timezone);
+                if ($timezone === '') {
+                    $timezone = 'UTC';
+                }
+                if (! app(TimezoneService::class)->isValid($timezone)) {
+                    Log::warning('TogglDateImporter: Invalid timezone', [
+                        'timezone' => $timezone,
+                    ]);
+                    $timezone = 'UTC';
+                }
+
                 $userId = $this->userImportHelper->getKey([
                     'email' => $workspaceUser->email,
                 ], [
                     'name' => $workspaceUser->name,
-                    'timezone' => $workspaceUser->timezone ?? 'UTC',
+                    'timezone' => $timezone,
                     'is_placeholder' => true,
                 ], (string) $workspaceUser->uid);
                 $this->memberImportHelper->getKey([
diff --git a/resources/testfiles/toggl_data_import_test_2/clients.json b/resources/testfiles/toggl_data_import_test_2/clients.json
new file mode 100644
index 00000000..1e1a8baa
--- /dev/null
+++ b/resources/testfiles/toggl_data_import_test_2/clients.json
@@ -0,0 +1,16 @@
+[
+    {
+        "archived": false,
+        "creator_id": 201,
+        "id": 301,
+        "name": "Big Company",
+        "wid": 0
+    },
+    {
+        "archived": true,
+        "creator_id": 201,
+        "id": 302,
+        "name": "Other Company (Archived)",
+        "wid": 0
+    }
+]
diff --git a/resources/testfiles/toggl_data_import_test_2/projects.json b/resources/testfiles/toggl_data_import_test_2/projects.json
new file mode 100644
index 00000000..0b0b3f3c
--- /dev/null
+++ b/resources/testfiles/toggl_data_import_test_2/projects.json
@@ -0,0 +1,86 @@
+[
+    {
+        "active": true,
+        "actual_hours": null,
+        "actual_seconds": null,
+        "auto_estimates": false,
+        "billable": false,
+        "cid": null,
+        "client_id": null,
+        "color": "#ef5350",
+        "currency": "EUR",
+        "estimated_hours": null,
+        "estimated_seconds": null,
+        "fixed_fee": null,
+        "guid": "",
+        "id": 401,
+        "is_private": true,
+        "name": "Project without Client",
+        "rate": null,
+        "rate_last_updated": null,
+        "recurring": false,
+        "recurring_parameters": null,
+        "start_date": "2020-01-01",
+        "status": "active",
+        "template": false,
+        "template_id": null,
+        "wid": 0,
+        "workspace_id": 0
+    },
+    {
+        "active": true,
+        "actual_hours": null,
+        "actual_seconds": null,
+        "auto_estimates": false,
+        "billable": true,
+        "cid": 301,
+        "client_id": 301,
+        "color": "#ec407a",
+        "currency": null,
+        "estimated_hours": null,
+        "estimated_seconds": null,
+        "fixed_fee": null,
+        "guid": "",
+        "id": 402,
+        "is_private": true,
+        "name": "Project for Big Company",
+        "rate": 100.01,
+        "rate_last_updated": null,
+        "recurring": false,
+        "recurring_parameters": null,
+        "start_date": "2020-01-01",
+        "status": "active",
+        "template": false,
+        "template_id": null,
+        "wid": 0,
+        "workspace_id": 0
+    },
+    {
+        "active": false,
+        "actual_hours": null,
+        "actual_seconds": null,
+        "auto_estimates": false,
+        "billable": true,
+        "cid": 302,
+        "client_id": 302,
+        "color": "#6a407f",
+        "currency": null,
+        "estimated_hours": null,
+        "estimated_seconds": null,
+        "fixed_fee": null,
+        "guid": "",
+        "id": 403,
+        "is_private": false,
+        "name": "Project (Archived)",
+        "rate": null,
+        "rate_last_updated": null,
+        "recurring": false,
+        "recurring_parameters": null,
+        "start_date": "2020-01-01",
+        "status": "active",
+        "template": false,
+        "template_id": null,
+        "wid": 0,
+        "workspace_id": 0
+    }
+]
diff --git a/resources/testfiles/toggl_data_import_test_2/projects_users/401.json b/resources/testfiles/toggl_data_import_test_2/projects_users/401.json
new file mode 100644
index 00000000..fe51488c
--- /dev/null
+++ b/resources/testfiles/toggl_data_import_test_2/projects_users/401.json
@@ -0,0 +1 @@
+[]
diff --git a/resources/testfiles/toggl_data_import_test_2/projects_users/402.json b/resources/testfiles/toggl_data_import_test_2/projects_users/402.json
new file mode 100644
index 00000000..134ff705
--- /dev/null
+++ b/resources/testfiles/toggl_data_import_test_2/projects_users/402.json
@@ -0,0 +1,14 @@
+[
+    {
+        "gid": null,
+        "group_id": null,
+        "id": 801,
+        "labour_cost": null,
+        "manager": true,
+        "project_id": 402,
+        "rate": 100.02,
+        "rate_last_updated": null,
+        "user_id": 2001,
+        "workspace_id": 0
+    }
+]
diff --git a/resources/testfiles/toggl_data_import_test_2/projects_users/403.json b/resources/testfiles/toggl_data_import_test_2/projects_users/403.json
new file mode 100644
index 00000000..fe51488c
--- /dev/null
+++ b/resources/testfiles/toggl_data_import_test_2/projects_users/403.json
@@ -0,0 +1 @@
+[]
diff --git a/resources/testfiles/toggl_data_import_test_2/tags.json b/resources/testfiles/toggl_data_import_test_2/tags.json
new file mode 100644
index 00000000..4bc90b57
--- /dev/null
+++ b/resources/testfiles/toggl_data_import_test_2/tags.json
@@ -0,0 +1,14 @@
+[
+    {
+        "creator_id": 0,
+        "id": 501,
+        "name": "Development",
+        "workspace_id": 0
+    },
+    {
+        "creator_id": 0,
+        "id": 502,
+        "name": "Backend",
+        "workspace_id": 0
+    }
+]
diff --git a/resources/testfiles/toggl_data_import_test_2/tasks/401.json b/resources/testfiles/toggl_data_import_test_2/tasks/401.json
new file mode 100644
index 00000000..fe51488c
--- /dev/null
+++ b/resources/testfiles/toggl_data_import_test_2/tasks/401.json
@@ -0,0 +1 @@
+[]
diff --git a/resources/testfiles/toggl_data_import_test_2/tasks/402.json b/resources/testfiles/toggl_data_import_test_2/tasks/402.json
new file mode 100644
index 00000000..844a67b8
--- /dev/null
+++ b/resources/testfiles/toggl_data_import_test_2/tasks/402.json
@@ -0,0 +1,24 @@
+[
+    {
+        "active": true,
+        "estimated_seconds": 0,
+        "id": 601,
+        "name": "Task 1",
+        "project_id": 402,
+        "recurring": false,
+        "tracked_seconds": 0,
+        "user_id": null,
+        "workspace_id": 0
+    },
+    {
+        "active": false,
+        "estimated_seconds": 0,
+        "id": 602,
+        "name": "Task 2",
+        "project_id": 403,
+        "recurring": false,
+        "tracked_seconds": 0,
+        "user_id": null,
+        "workspace_id": 0
+    }
+]
diff --git a/resources/testfiles/toggl_data_import_test_2/tasks/403.json b/resources/testfiles/toggl_data_import_test_2/tasks/403.json
new file mode 100644
index 00000000..fe51488c
--- /dev/null
+++ b/resources/testfiles/toggl_data_import_test_2/tasks/403.json
@@ -0,0 +1 @@
+[]
diff --git a/resources/testfiles/toggl_data_import_test_2/workspace_users.json b/resources/testfiles/toggl_data_import_test_2/workspace_users.json
new file mode 100644
index 00000000..b8456708
--- /dev/null
+++ b/resources/testfiles/toggl_data_import_test_2/workspace_users.json
@@ -0,0 +1,19 @@
+[
+    {
+        "active": true,
+        "admin": true,
+        "email": "peter.test@email.test",
+        "group_ids": [],
+        "id": 201,
+        "inactive": false,
+        "labour_cost": null,
+        "name": "Peter Tester",
+        "rate": null,
+        "rate_last_updated": null,
+        "role": "admin",
+        "timezone": "Etc/UTC",
+        "uid": 2001,
+        "wid": 0,
+        "working_hours_in_minutes": null
+    }
+]
diff --git a/tests/Unit/Service/Import/Importers/TogglDataImporterTest.php b/tests/Unit/Service/Import/Importers/TogglDataImporterTest.php
index ec36899c..fc5505e1 100644
--- a/tests/Unit/Service/Import/Importers/TogglDataImporterTest.php
+++ b/tests/Unit/Service/Import/Importers/TogglDataImporterTest.php
@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace Tests\Unit\Service\Import\Importers;
 
 use App\Models\Organization;
+use App\Models\User;
 use App\Service\Import\Importers\DefaultImporter;
 use App\Service\Import\Importers\ImportException;
 use App\Service\Import\Importers\TogglDataImporter;
@@ -88,4 +89,30 @@ class TogglDataImporterTest extends ImporterTestAbstract
         $this->assertSame(0, $report->projectsCreated);
         $this->assertSame(0, $report->clientsCreated);
     }
+
+    public function test_import_of_user_with_unknown_timezone_will_be_mapped_to_utc(): void
+    {
+        // Arrange
+        $zipPath = $this->createTestZip('toggl_data_import_test_2');
+        $timezone = 'Europe/Vienna';
+        $organization = Organization::factory()->create();
+        $importer = new TogglDataImporter;
+        $importer->init($organization);
+        $data = file_get_contents($zipPath);
+
+        // Act
+        $importer->importData($data, $timezone);
+        $report = $importer->getReport();
+
+        // Assert
+        $this->assertSame(0, $report->timeEntriesCreated);
+        $this->assertSame(2, $report->tagsCreated);
+        $this->assertSame(2, $report->tasksCreated);
+        $this->assertSame(1, $report->usersCreated);
+        $this->assertSame(3, $report->projectsCreated);
+        $this->assertSame(2, $report->clientsCreated);
+        $user = User::query()->where('email', '=', 'peter.test@email.test')->first();
+        $this->assertSame('UTC', $user->timezone);
+        $this->assertTrue($user->is_placeholder);
+    }
 }