diff --git a/doc/source/reference/offset_frequency.rst b/doc/source/reference/offset_frequency.rst
index fed23e48e43e9..ee89df3114048 100644
--- a/doc/source/reference/offset_frequency.rst
+++ b/doc/source/reference/offset_frequency.rst
@@ -59,6 +59,9 @@ Properties
     BusinessDay.normalize
     BusinessDay.rule_code
     BusinessDay.n
+    BusinessDay.weekmask
+    BusinessDay.holidays
+    BusinessDay.calendar
 
 Methods
 ~~~~~~~
@@ -95,6 +98,9 @@ Properties
     BusinessHour.n
     BusinessHour.start
     BusinessHour.end
+    BusinessHour.weekmask
+    BusinessHour.holidays
+    BusinessHour.calendar
 
 Methods
 ~~~~~~~
@@ -128,6 +134,9 @@ Properties
     CustomBusinessDay.normalize
     CustomBusinessDay.rule_code
     CustomBusinessDay.n
+    CustomBusinessDay.weekmask
+    CustomBusinessDay.calendar
+    CustomBusinessDay.holidays
 
 Methods
 ~~~~~~~
@@ -162,6 +171,9 @@ Properties
     CustomBusinessHour.normalize
     CustomBusinessHour.rule_code
     CustomBusinessHour.n
+    CustomBusinessHour.weekmask
+    CustomBusinessHour.calendar
+    CustomBusinessHour.holidays
     CustomBusinessHour.start
     CustomBusinessHour.end
 
@@ -334,6 +346,9 @@ Properties
     CustomBusinessMonthEnd.normalize
     CustomBusinessMonthEnd.rule_code
     CustomBusinessMonthEnd.n
+    CustomBusinessMonthEnd.weekmask
+    CustomBusinessMonthEnd.calendar
+    CustomBusinessMonthEnd.holidays
 
 Methods
 ~~~~~~~
@@ -368,6 +383,9 @@ Properties
     CustomBusinessMonthBegin.normalize
     CustomBusinessMonthBegin.rule_code
     CustomBusinessMonthBegin.n
+    CustomBusinessMonthBegin.weekmask
+    CustomBusinessMonthBegin.calendar
+    CustomBusinessMonthBegin.holidays
 
 Methods
 ~~~~~~~
@@ -1241,6 +1259,9 @@ Properties
     BDay.offset
     BDay.rule_code
     BDay.n
+    BDay.weekmask
+    BDay.holidays
+    BDay.calendar
 
 Methods
 ~~~~~~~
@@ -1356,6 +1377,9 @@ Properties
     CBMonthEnd.offset
     CBMonthEnd.rule_code
     CBMonthEnd.n
+    CBMonthEnd.weekmask
+    CBMonthEnd.holidays
+    CBMonthEnd.calendar
 
 Methods
 ~~~~~~~
@@ -1397,6 +1421,9 @@ Properties
     CBMonthBegin.offset
     CBMonthBegin.rule_code
     CBMonthBegin.n
+    CBMonthBegin.weekmask
+    CBMonthBegin.holidays
+    CBMonthBegin.calendar
 
 Methods
 ~~~~~~~
@@ -1435,6 +1462,9 @@ Properties
     CDay.offset
     CDay.rule_code
     CDay.n
+    CDay.weekmask
+    CDay.calendar
+    CDay.holidays
 
 Methods
 ~~~~~~~
@@ -1452,6 +1482,7 @@ Methods
     CDay.rollforward
     CDay.__call__
 
+
 .. _api.frequencies:
 
 ===========
diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 660cd3af1b35e..8e5634253bd39 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1247,11 +1247,27 @@ cdef class BusinessMixin(SingleConstructorOffset):
 
     cdef readonly:
         timedelta _offset
+        # Only Custom subclasses use weekmask, holiday, calendar
+        object weekmask, holidays, calendar
 
     def __init__(self, n=1, normalize=False, offset=timedelta(0)):
         BaseOffset.__init__(self, n, normalize)
         self._offset = offset
 
+    cpdef _init_custom(self, weekmask, holidays, calendar):
+        """
+        Additional __init__ for Custom subclasses.
+        """
+        calendar, holidays = _get_calendar(
+            weekmask=weekmask, holidays=holidays, calendar=calendar
+        )
+        # Custom offset instances are identified by the
+        # following two attributes. See DateOffset._params()
+        # holidays, weekmask
+        self.weekmask = weekmask
+        self.holidays = holidays
+        self.calendar = calendar
+
     @property
     def offset(self):
         """
@@ -1276,6 +1292,18 @@ cdef class BusinessMixin(SingleConstructorOffset):
             self._offset = state.pop("_offset")
         elif "offset" in state:
             self._offset = state.pop("offset")
+
+        if self._prefix.startswith("C"):
+            # i.e. this is a Custom class
+            weekmask = state.pop("weekmask")
+            holidays = state.pop("holidays")
+            calendar, holidays = _get_calendar(weekmask=weekmask,
+                                               holidays=holidays,
+                                               calendar=None)
+            self.weekmask = weekmask
+            self.calendar = calendar
+            self.holidays = holidays
+
         BaseOffset.__setstate__(self, state)
 
 
@@ -1785,25 +1813,6 @@ cdef class BusinessHour(BusinessMixin):
             return False
 
 
-class CustomMixin:
-    """
-    Mixin for classes that define and validate calendar, holidays,
-    and weekdays attributes.
-    """
-
-    def __init__(self, weekmask, holidays, calendar):
-        calendar, holidays = _get_calendar(
-            weekmask=weekmask, holidays=holidays, calendar=calendar
-        )
-        # Custom offset instances are identified by the
-        # following two attributes. See DateOffset._params()
-        # holidays, weekmask
-
-        object.__setattr__(self, "weekmask", weekmask)
-        object.__setattr__(self, "holidays", holidays)
-        object.__setattr__(self, "calendar", calendar)
-
-
 cdef class WeekOfMonthMixin(SingleConstructorOffset):
     """
     Mixin for methods common to WeekOfMonth and LastWeekOfMonth.
@@ -3252,7 +3261,7 @@ cdef class Easter(SingleConstructorOffset):
 # Custom Offset classes
 
 
-class CustomBusinessDay(CustomMixin, BusinessDay):
+cdef class CustomBusinessDay(BusinessDay):
     """
     DateOffset subclass representing custom business days excluding holidays.
 
@@ -3291,12 +3300,12 @@ class CustomBusinessDay(CustomMixin, BusinessDay):
         offset=timedelta(0),
     ):
         BusinessDay.__init__(self, n, normalize, offset)
-        CustomMixin.__init__(self, weekmask, holidays, calendar)
+        self._init_custom(weekmask, holidays, calendar)
 
-    def __setstate__(self, state):
+    cpdef __setstate__(self, state):
         self.holidays = state.pop("holidays")
         self.weekmask = state.pop("weekmask")
-        super().__setstate__(state)
+        BusinessDay.__setstate__(self, state)
 
     @apply_wraps
     def apply(self, other):
@@ -3338,7 +3347,7 @@ class CustomBusinessDay(CustomMixin, BusinessDay):
         return np.is_busday(day64, busdaycal=self.calendar)
 
 
-class CustomBusinessHour(CustomMixin, BusinessHour):
+class CustomBusinessHour(BusinessHour):
     """
     DateOffset subclass representing possibly n custom business days.
     """
@@ -3361,7 +3370,7 @@ class CustomBusinessHour(CustomMixin, BusinessHour):
         offset=timedelta(0),
     ):
         BusinessHour.__init__(self, n, normalize, start=start, end=end, offset=offset)
-        CustomMixin.__init__(self, weekmask, holidays, calendar)
+        self._init_custom(weekmask, holidays, calendar)
 
     def __reduce__(self):
         # None for self.calendar bc np.busdaycalendar doesnt pickle nicely
@@ -3380,7 +3389,7 @@ class CustomBusinessHour(CustomMixin, BusinessHour):
         )
 
 
-class _CustomBusinessMonth(CustomMixin, BusinessMixin, MonthOffset):
+class _CustomBusinessMonth(BusinessMixin, MonthOffset):
     """
     DateOffset subclass representing custom business month(s).
 
@@ -3420,7 +3429,7 @@ class _CustomBusinessMonth(CustomMixin, BusinessMixin, MonthOffset):
         offset=timedelta(0),
     ):
         BusinessMixin.__init__(self, n, normalize, offset)
-        CustomMixin.__init__(self, weekmask, holidays, calendar)
+        self._init_custom(weekmask, holidays, calendar)
 
     def __reduce__(self):
         # None for self.calendar bc np.busdaycalendar doesnt pickle nicely