diff --git a/docs/changelog/2768.bugfix.rst b/docs/changelog/2768.bugfix.rst
new file mode 100644
index 000000000..80623b624
--- /dev/null
+++ b/docs/changelog/2768.bugfix.rst
@@ -0,0 +1 @@
+Fix logging error with emoji in git branch name.
diff --git a/src/tox/pytest.py b/src/tox/pytest.py
index 21cd816ad..ae2112525 100644
--- a/src/tox/pytest.py
+++ b/src/tox/pytest.py
@@ -161,7 +161,7 @@ def _setup_files(dest: Path, base: Path | None, content: dict[str, Any]) -> None
                 at_path.mkdir(exist_ok=True)
                 ToxProject._setup_files(at_path, None, value)
             elif isinstance(value, str):
-                at_path.write_text(textwrap.dedent(value))
+                at_path.write_text(textwrap.dedent(value), encoding="utf-8")
             elif value is None:
                 at_path.mkdir()
             else:
diff --git a/src/tox/tox_env/api.py b/src/tox/tox_env/api.py
index 98c4501a9..3ce15b993 100644
--- a/src/tox/tox_env/api.py
+++ b/src/tox/tox_env/api.py
@@ -444,7 +444,7 @@ def _log_execute(self, request: ExecuteRequest, status: ExecuteStatus) -> None:
 
     @staticmethod
     def _write_execute_log(env_name: str, log_file: Path, request: ExecuteRequest, status: ExecuteStatus) -> None:
-        with log_file.open("wt") as file:
+        with log_file.open("wt", encoding="utf-8") as file:
             file.write(f"name: {env_name}\n")
             file.write(f"run_id: {request.run_id}\n")
             for env_key, env_value in request.env.items():
diff --git a/tests/tox_env/test_tox_env_api.py b/tests/tox_env/test_tox_env_api.py
index f4f286078..1a8fefdc0 100644
--- a/tests/tox_env/test_tox_env_api.py
+++ b/tests/tox_env/test_tox_env_api.py
@@ -34,7 +34,8 @@ def test_allow_list_external_fail(tox_project: ToxProjectCreator, fake_exe_on_pa
 
 def test_env_log(tox_project: ToxProjectCreator) -> None:
     cmd = "commands=python -c 'import sys; print(1); print(2); print(3, file=sys.stderr); print(4, file=sys.stderr)'"
-    prj = tox_project({"tox.ini": f"[testenv]\npackage=skip\n{cmd}"})
+    env_vars = "    UNPREDICTABLE = 🪟"
+    prj = tox_project({"tox.ini": f"[testenv]\npackage=skip\nset_env =\n{env_vars}\n{cmd}"})
     result_first = prj.run("r")
     result_first.assert_success()