diff --git a/doc/whats-new.rst b/doc/whats-new.rst
index 9c16fb74a7b..735159fb33a 100644
--- a/doc/whats-new.rst
+++ b/doc/whats-new.rst
@@ -38,6 +38,8 @@ Deprecations
 
 Bug fixes
 ~~~~~~~~~
+- Added support for `numpy.bool_` attributes in roundtrips using `h5netcdf` engine with `invalid_netcdf=True` [which casts `bool`s to `numpy.bool_`] (:issue:`4981`, :pull:`4986`).
+  By `Victor Negîrneac <https://github.com/caenrigen>`_.
 - Don't allow passing ``axis`` to :py:meth:`Dataset.reduce` methods (:issue:`3510`, :pull:`4940`).
   By `Justus Magin <https://github.com/keewis>`_.
 
diff --git a/xarray/backends/api.py b/xarray/backends/api.py
index 4fa34b39925..aca6524a3bd 100644
--- a/xarray/backends/api.py
+++ b/xarray/backends/api.py
@@ -199,12 +199,21 @@ def check_name(name):
         check_name(k)
 
 
-def _validate_attrs(dataset):
+def _validate_attrs(dataset, invalid_netcdf=False):
     """`attrs` must have a string key and a value which is either: a number,
-    a string, an ndarray or a list/tuple of numbers/strings.
+    a string, an ndarray, a list/tuple of numbers/strings, or a numpy.bool_.
+
+    Notes
+    -----
+    A numpy.bool_ is only allowed when using the h5netcdf engine with
+    `invalid_netcdf=True`.
     """
 
-    def check_attr(name, value):
+    valid_types = (str, Number, np.ndarray, np.number, list, tuple)
+    if invalid_netcdf:
+        valid_types += (np.bool_,)
+
+    def check_attr(name, value, valid_types):
         if isinstance(name, str):
             if not name:
                 raise ValueError(
@@ -218,22 +227,21 @@ def check_attr(name, value):
                 "serialization to netCDF files"
             )
 
-        if not isinstance(value, (str, Number, np.ndarray, np.number, list, tuple)):
+        if not isinstance(value, valid_types):
             raise TypeError(
-                f"Invalid value for attr {name!r}: {value!r} must be a number, "
-                "a string, an ndarray or a list/tuple of "
-                "numbers/strings for serialization to netCDF "
-                "files"
+                f"Invalid value for attr {name!r}: {value!r}. For serialization to "
+                "netCDF files, its value must be of one of the following types: "
+                f"{', '.join([vtype.__name__ for vtype in valid_types])}"
             )
 
     # Check attrs on the dataset itself
     for k, v in dataset.attrs.items():
-        check_attr(k, v)
+        check_attr(k, v, valid_types)
 
     # Check attrs on each variable within the dataset
     for variable in dataset.variables.values():
         for k, v in variable.attrs.items():
-            check_attr(k, v)
+            check_attr(k, v, valid_types)
 
 
 def _protect_dataset_variables_inplace(dataset, cache):
@@ -1056,7 +1064,7 @@ def to_netcdf(
 
     # validate Dataset keys, DataArray names, and attr keys/values
     _validate_dataset_names(dataset)
-    _validate_attrs(dataset)
+    _validate_attrs(dataset, invalid_netcdf=invalid_netcdf and engine == "h5netcdf")
 
     try:
         store_open = WRITEABLE_STORES[engine]
diff --git a/xarray/tests/test_backends.py b/xarray/tests/test_backends.py
index d15736e608d..f6c00a2a9a9 100644
--- a/xarray/tests/test_backends.py
+++ b/xarray/tests/test_backends.py
@@ -2541,6 +2541,14 @@ def test_complex(self, invalid_netcdf, warntype, num_warns):
 
         assert recorded_num_warns == num_warns
 
+    def test_numpy_bool_(self):
+        # h5netcdf loads booleans as numpy.bool_, this type needs to be supported
+        # when writing invalid_netcdf datasets in order to support a roundtrip
+        expected = Dataset({"x": ("y", np.ones(5), {"numpy_bool": np.bool_(True)})})
+        save_kwargs = {"invalid_netcdf": True}
+        with self.roundtrip(expected, save_kwargs=save_kwargs) as actual:
+            assert_identical(expected, actual)
+
     def test_cross_engine_read_write_netcdf4(self):
         # Drop dim3, because its labels include strings. These appear to be
         # not properly read with python-netCDF4, which converts them into