diff --git a/lms/djangoapps/edxnotes/decorators.py b/lms/djangoapps/edxnotes/decorators.py
index 39d5c0b076d4..866df4915999 100644
--- a/lms/djangoapps/edxnotes/decorators.py
+++ b/lms/djangoapps/edxnotes/decorators.py
@@ -22,7 +22,15 @@ def get_html(self, *args, **kwargs):
         Returns raw html for the component.
         """
         # Import is placed here to avoid model import at project startup.
-        from .helpers import generate_uid, get_edxnotes_id_token, get_public_endpoint, get_token_url, is_feature_enabled
+        from .helpers import (
+            generate_uid,
+            get_ccx_master_course_key,
+            get_ccx_master_usage_key,
+            get_edxnotes_id_token,
+            get_public_endpoint,
+            get_token_url,
+            is_feature_enabled,
+        )
 
         if not settings.ENABLE_EDXNOTES:
             return original_get_html(self, *args, **kwargs)
@@ -47,6 +55,14 @@ def get_html(self, *args, **kwargs):
         if is_studio or not is_feature_enabled(course, user):
             return original_get_html(self, *args, **kwargs)
         else:
+            # Notes are recorded against the master course (and its own block ids),
+            # not the CCX, so a note taken in any CCX section shows up in every CCX
+            # section derived from the same master course. `tokenUrl` deliberately
+            # keeps the real (CCX) course id: that URL is routed/access-checked
+            # against the course actually being viewed, not the note's data key.
+            notes_course_id = get_ccx_master_course_key(course.id)
+            notes_usage_id = get_ccx_master_usage_key(self.scope_ids.usage_id)
+
             return render_to_string("edxnotes_wrapper.html", {
                 "content": original_get_html(self, *args, **kwargs),
                 "uid": generate_uid(),
@@ -55,8 +71,8 @@ def get_html(self, *args, **kwargs):
                 ),
                 "params": {
                     # Use camelCase to name keys.
-                    "usageId": self.scope_ids.usage_id,
-                    "courseId": course.id,
+                    "usageId": notes_usage_id,
+                    "courseId": notes_course_id,
                     "token": get_edxnotes_id_token(user),
                     "tokenUrl": get_token_url(course.id),
                     "endpoint": get_public_endpoint(),
diff --git a/lms/djangoapps/edxnotes/helpers.py b/lms/djangoapps/edxnotes/helpers.py
index ad7a7af15eeb..0726a807fa2e 100644
--- a/lms/djangoapps/edxnotes/helpers.py
+++ b/lms/djangoapps/edxnotes/helpers.py
@@ -74,6 +74,37 @@ def get_token_url(course_id):
     })
 
 
+def get_ccx_master_course_key(course_key):
+    """
+    If `course_key` identifies a CCX (Custom Course for edX), return the CourseKey
+    of the CCX's master course. Otherwise return `course_key` unchanged.
+
+    This lets notes/annotations created while viewing a CCX be recorded against the
+    shared master course rather than that one CCX section, so the same user sees the
+    same notes on every CCX section (and the master course itself) derived from it.
+    """
+    ccx_id = getattr(course_key, 'ccx', None)
+    if not ccx_id:
+        return course_key
+
+    # Imported locally to avoid a hard import-time dependency between the edxnotes
+    # and ccx apps.
+    from lms.djangoapps.ccx.utils import get_ccx_from_ccx_locator  # pylint: disable=import-outside-toplevel
+    ccx = get_ccx_from_ccx_locator(course_key)
+    return ccx.course_id if ccx else course_key
+
+
+def get_ccx_master_usage_key(usage_key):
+    """
+    If `usage_key` identifies a block within a CCX, return the equivalent UsageKey
+    for the same block within the CCX's master course (CCX field overrides and
+    scheduling don't change the underlying content, so the block ids line up).
+    Otherwise return `usage_key` unchanged.
+    """
+    to_block_locator = getattr(usage_key, 'to_block_locator', None)
+    return to_block_locator() if to_block_locator else usage_key
+
+
 def send_request(user, course_id, page, page_size, path="", text=None):
     """
     Sends a request to notes api with appropriate parameters and headers.
@@ -332,7 +363,10 @@ def get_notes(request, course, page=DEFAULT_PAGE, page_size=DEFAULT_PAGE_SIZE, t
             results: list with notes info dictionary. each item in this list will be a dict
     """
     path = 'search' if text else 'annotations'
-    response = send_request(request.user, course.id, page, page_size, path, text)
+    # Resolve to the master course so notes taken inside any CCX section are
+    # recorded against (and read back from) the shared master course.
+    notes_course_id = get_ccx_master_course_key(course.id)
+    response = send_request(request.user, notes_course_id, page, page_size, path, text)
 
     try:
         collection = json.loads(response.content.decode('utf-8'))