diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 7988012498db7..b6df108a3166c 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -69,6 +69,7 @@ repos:
     rev: v1.2.2
     hooks:
     -   id: yesqa
+        additional_dependencies: [flake8==3.9.0]
 -   repo: local
     hooks:
     -   id: flake8-rst
@@ -164,6 +165,13 @@ repos:
         files: ^(environment.yml|requirements-dev.txt)$
         pass_filenames: false
         additional_dependencies: [pyyaml]
+    -   id: sync-flake8-versions
+        name: Check flake8 version is synced across flake8, yesqa, and environment.yml
+        language: python
+        entry: python scripts/sync_flake8_versions.py
+        files: ^(\.pre-commit-config\.yaml|environment\.yml)$
+        pass_filenames: false
+        additional_dependencies: [pyyaml]
     -   id: title-capitalization
         name: Validate correct capitalization among titles in documentation
         entry: python scripts/validate_rst_title_capitalization.py
diff --git a/environment.yml b/environment.yml
index b942adb764104..2849297abf3ac 100644
--- a/environment.yml
+++ b/environment.yml
@@ -20,7 +20,7 @@ dependencies:
   # code checks
   - black=20.8b1
   - cpplint
-  - flake8
+  - flake8=3.9.0
   - flake8-bugbear>=21.3.2  # used by flake8, find likely bugs
   - flake8-comprehensions>=3.1.0  # used by flake8, linting of unnecessary comprehensions
   - isort>=5.2.1  # check that imports are in the right order
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 094456eb85c9a..966cf50d4fbac 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -8,7 +8,7 @@ asv
 cython>=0.29.21
 black==20.8b1
 cpplint
-flake8
+flake8==3.9.0
 flake8-bugbear>=21.3.2
 flake8-comprehensions>=3.1.0
 isort>=5.2.1
diff --git a/scripts/sync_flake8_versions.py b/scripts/sync_flake8_versions.py
new file mode 100644
index 0000000000000..8dd7abcf47f02
--- /dev/null
+++ b/scripts/sync_flake8_versions.py
@@ -0,0 +1,101 @@
+"""
+Check that the flake8 pins are the same in:
+
+- environment.yml
+- .pre-commit-config.yaml, in the flake8 hook
+- .pre-commit-config.yaml, in the additional dependencies of the yesqa hook
+
+The flake8 hook revision in .pre-commit-config.yaml is taken as the reference revision.
+
+Usage: either
+
+- ``python scripts/sync_flake8_versions.py``, or
+- ``pre-commit run sync-flake8-versions --all-files``.
+"""
+import sys
+from typing import (
+    Any,
+    Mapping,
+    NamedTuple,
+    Sequence,
+    Tuple,
+    TypeVar,
+)
+
+import yaml
+
+
+class Revisions(NamedTuple):
+    precommit_rev: str
+    precommit_yesqa_rev: str
+    environment_rev: str
+
+
+YamlMapping = Mapping[str, Any]
+Repo = TypeVar("Repo", bound=YamlMapping)
+
+
+def _get_repo_hook(repos: Sequence[Repo], hook_name: str) -> Tuple[Repo, YamlMapping]:
+    for repo in repos:
+        for hook in repo["hooks"]:
+            if hook["id"] == hook_name:
+                return repo, hook
+    else:
+        raise RuntimeError(f"Repo with hook {hook_name} not found")
+
+
+def get_revisions(precommit_config: YamlMapping, environment: YamlMapping) -> Revisions:
+    repos = precommit_config["repos"]
+    flake8_repo, _ = _get_repo_hook(repos, "flake8")
+    precommit_rev = flake8_repo["rev"]
+
+    _, yesqa_hook = _get_repo_hook(repos, "yesqa")
+    additional_dependencies = yesqa_hook.get("additional_dependencies", [])
+    for dep in additional_dependencies:
+        if "==" in dep:
+            pkg, rev = dep.split("==", maxsplit=1)
+            if pkg == "flake8":
+                precommit_yesqa_rev = rev
+                break
+    else:
+        raise RuntimeError(
+            "flake8 not found, or not pinned, in additional dependencies of yesqa "
+            "hook in .pre-commit-config.yaml"
+        )
+
+    deps = environment["dependencies"]
+    for dep in deps:
+        if isinstance(dep, str) and "=" in dep:
+            pkg, rev = dep.split("=", maxsplit=1)
+            if pkg == "flake8":
+                environment_rev = rev
+                break
+    else:
+        raise RuntimeError("flake8 not found, or not pinned, in environment.yml")
+
+    return Revisions(precommit_rev, precommit_yesqa_rev, environment_rev)
+
+
+if __name__ == "__main__":
+    with open(".pre-commit-config.yaml") as fd:
+        precommit_config = yaml.safe_load(fd)
+    with open("environment.yml") as fd:
+        environment = yaml.safe_load(fd)
+
+    revisions = get_revisions(precommit_config, environment)
+
+    if revisions.environment_rev != revisions.precommit_rev:
+        sys.stdout.write(
+            f"flake8 pin in environment.yml is {revisions.environment_rev}, "
+            f"should be {revisions.precommit_rev}\n"
+        )
+        sys.exit(1)
+
+    if revisions.precommit_yesqa_rev != revisions.precommit_rev:
+        sys.stdout.write(
+            f"flake8 pin in yesqa is {revisions.precommit_yesqa_rev}, "
+            f"should be {revisions.precommit_rev}\n"
+        )
+        sys.exit(1)
+
+    sys.exit(0)
diff --git a/scripts/tests/test_sync_flake8_versions.py b/scripts/tests/test_sync_flake8_versions.py
new file mode 100644
index 0000000000000..fc559f3e5e982
--- /dev/null
+++ b/scripts/tests/test_sync_flake8_versions.py
@@ -0,0 +1,25 @@
+from ..sync_flake8_versions import (
+    Revisions,
+    get_revisions,
+)
+
+
+def test_get_revisions():
+    precommit_config = {
+        "repos": [
+            {
+                "repo": "https://gitlab.com/pycqa/flake8",
+                "rev": "foo",
+                "hooks": [{"id": "flake8"}],
+            },
+            {
+                "repo": "https://github.com/asottile/yesqa",
+                "rev": "v1.2.2",
+                "hooks": [{"id": "yesqa", "additional_dependencies": ["flake8==bar"]}],
+            },
+        ]
+    }
+    environment = {"dependencies": ["flake8=qux"]}
+    result = get_revisions(precommit_config, environment)
+    expected = Revisions("foo", "bar", "qux")
+    assert result == expected