diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 525c069..362046c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -21,3 +21,25 @@ jobs:
 
       - name: Test
         run: ctest --test-dir build --output-on-failure
+
+  project-validator:
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/checkout@v4
+        with:
+          repository: cpp-best-practices/project_validator
+          ref: main
+          path: project_validator
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.14"
+
+      - name: Install validator dependencies
+        run: python -m pip install "PyYAML>=6.0"
+
+      - name: Validate project
+        working-directory: project_validator
+        run: python -m project_validator --build --exclude project_validator ${{ github.workspace }}
diff --git a/tests/test_ci_workflow.py b/tests/test_ci_workflow.py
new file mode 100644
index 0000000..d45c380
--- /dev/null
+++ b/tests/test_ci_workflow.py
@@ -0,0 +1,57 @@
+#!/usr/bin/env python3
+"""Unit tests for .github/workflows/ci.yml."""
+
+from __future__ import annotations
+
+import re
+import unittest
+from pathlib import Path
+
+WORKFLOW = Path(__file__).resolve().parent.parent / ".github" / "workflows" / "ci.yml"
+VALIDATOR_JOB = "project-validator"
+JOB_HEADER = re.compile(r"^  (?P<name>[A-Za-z0-9_-]+):\s*$")
+
+
+def workflow_jobs(text: str) -> dict[str, str]:
+    """Each job under `jobs:`, keyed by name, with its indented body."""
+    jobs: dict[str, list[str]] = {}
+    current: list[str] | None = None
+    in_jobs = False
+    for line in text.splitlines():
+        if not line.startswith(" ") and line.strip():
+            in_jobs = line.rstrip() == "jobs:"
+            current = None
+            continue
+        header = JOB_HEADER.match(line) if in_jobs else None
+        if header is not None:
+            current = jobs.setdefault(header.group("name"), [])
+        elif current is not None:
+            current.append(line)
+    return {name: "\n".join(body) for name, body in jobs.items()}
+
+
+class ProjectValidatorJobTest(unittest.TestCase):
+    def setUp(self) -> None:
+        self.jobs = workflow_jobs(WORKFLOW.read_text(encoding="utf-8"))
+
+    def validator_job(self) -> str:
+        self.assertIn(VALIDATOR_JOB, self.jobs, f"{WORKFLOW} has no {VALIDATOR_JOB} job")
+        return self.jobs[VALIDATOR_JOB]
+
+    def test_checks_out_the_validator_main_branch(self) -> None:
+        job = self.validator_job()
+        self.assertRegex(job, re.compile(r"^\s+repository:\s*cpp-best-practices/project_validator\s*$", re.M))
+        self.assertRegex(job, re.compile(r"^\s+ref:\s*main\s*$", re.M))
+
+    def test_runs_the_validator_on_this_project(self) -> None:
+        self.assertRegex(self.validator_job(), r"-m project_validator\b.*\$\{\{\s*github\.workspace\s*\}\}")
+
+
+class WorkflowJobsTest(unittest.TestCase):
+    def test_splits_jobs_by_name(self) -> None:
+        text = "name: ci\njobs:\n  first:\n    runs-on: a\n  second:\n    runs-on: b\nother:\n  third:\n"
+        self.assertEqual(workflow_jobs(text), {"first": "    runs-on: a", "second": "    runs-on: b"})
+
+
+if __name__ == "__main__":
+    unittest.main()