diff --git a/README.md b/README.md
index 7fe76a1e7..fe2785b9b 100644
--- a/README.md
+++ b/README.md
@@ -116,6 +116,9 @@ Migrations for 'admin':
   - `extra()`
   - `select_related()`
 
+- `Subquery`, `Exists`, and using a `QuerySet` in `QuerySet.annotate()` aren't
+  supported.
+
 - Queries with joins aren't supported.
 
 - `DateTimeField` doesn't support microsecond precision, and correspondingly,
diff --git a/django_mongodb/expressions.py b/django_mongodb/expressions.py
index f08e6c666..d00c3e295 100644
--- a/django_mongodb/expressions.py
+++ b/django_mongodb/expressions.py
@@ -3,15 +3,18 @@
 
 from bson import Decimal128
 from django.core.exceptions import EmptyResultSet, FullResultSet
+from django.db import NotSupportedError
 from django.db.models.expressions import (
     Case,
     Col,
     CombinedExpression,
     ExpressionWrapper,
     NegatedExpression,
+    Subquery,
     Value,
     When,
 )
+from django.db.models.sql import Query
 
 
 def case(self, compiler, connection):
@@ -59,6 +62,14 @@ def negated_expression(self, compiler, connection):
     return {"$not": expression_wrapper(self, compiler, connection)}
 
 
+def query(self, compiler, connection):  # noqa: ARG001
+    raise NotSupportedError("Using a QuerySet in annotate() is not supported on MongoDB.")
+
+
+def subquery(self, compiler, connection):  # noqa: ARG001
+    raise NotSupportedError(f"{self.__class__.__name__} is not supported on MongoDB.")
+
+
 def when(self, compiler, connection):
     return self.condition.as_mql(compiler, connection)
 
@@ -82,5 +93,7 @@ def register_expressions():
     CombinedExpression.as_mql = combined_expression
     ExpressionWrapper.as_mql = expression_wrapper
     NegatedExpression.as_mql = negated_expression
+    Query.as_mql = query
+    Subquery.as_mql = subquery
     When.as_mql = when
     Value.as_mql = value
diff --git a/django_mongodb/features.py b/django_mongodb/features.py
index 7779d886d..1eaf9130e 100644
--- a/django_mongodb/features.py
+++ b/django_mongodb/features.py
@@ -59,10 +59,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         # the result back to UTC.
         "db_functions.datetime.test_extract_trunc.DateFunctionWithTimeZoneTests.test_trunc_func_with_timezone",
         "db_functions.datetime.test_extract_trunc.DateFunctionWithTimeZoneTests.test_trunc_timezone_applied_before_truncation",
-        # pk__in=queryset doesn't work because subqueries aren't a thing in
-        # MongoDB.
-        "annotations.tests.NonAggregateAnnotationTestCase.test_annotation_and_alias_filter_in_subquery",
-        "model_fields.test_jsonfield.TestQuerying.test_usage_in_subquery",
         # Length of null considered zero rather than null.
         "db_functions.text.test_length.LengthTests.test_basic",
         # Key transforms are incorrectly treated as joins:
@@ -220,25 +216,11 @@ def django_test_expected_failures(self):
             "timezones.tests.NewDatabaseTests.test_query_aggregation",
         },
         "QuerySet.annotate() has some limitations.": {
-            # Exists not supported.
-            "annotations.tests.NonAggregateAnnotationTestCase.test_annotation_exists_none_query",
-            "lookup.tests.LookupTests.test_exact_exists",
-            "lookup.tests.LookupTests.test_nested_outerref_lhs",
-            "lookup.tests.LookupQueryingTests.test_filter_exists_lhs",
             # annotate() with combined expressions doesn't work:
             # 'WhereNode' object has no attribute 'field'
             "lookup.tests.LookupQueryingTests.test_combined_annotated_lookups_in_filter",
             "lookup.tests.LookupQueryingTests.test_combined_annotated_lookups_in_filter_false",
             "lookup.tests.LookupQueryingTests.test_combined_lookups",
-            # Subquery not supported.
-            "annotations.tests.NonAggregateAnnotationTestCase.test_empty_queryset_annotation",
-            "db_functions.comparison.test_coalesce.CoalesceTests.test_empty_queryset",
-            "db_functions.datetime.test_extract_trunc.DateFunctionTests.test_extract_outerref",
-            "db_functions.datetime.test_extract_trunc.DateFunctionTests.test_trunc_subquery_with_parameters",
-            "expressions_case.tests.CaseExpressionTests.test_in_subquery",
-            "lookup.tests.LookupQueryingTests.test_filter_subquery_lhs",
-            "model_fields.test_jsonfield.TestQuerying.test_nested_key_transform_on_subquery",
-            "model_fields.test_jsonfield.TestQuerying.test_obj_subquery_lookup",
             # Invalid $project :: caused by :: Unknown expression $count,
             "annotations.tests.NonAggregateAnnotationTestCase.test_combined_expression_annotation_with_aggregation",
             "annotations.tests.NonAggregateAnnotationTestCase.test_combined_f_expression_annotation_with_aggregation",
@@ -263,6 +245,28 @@ def django_test_expected_failures(self):
             # annotate().filter().count() gives incorrect results.
             "db_functions.datetime.test_extract_trunc.DateFunctionTests.test_extract_year_exact_lookup",
         },
+        "Exists is not supported on MongoDB.": {
+            "annotations.tests.NonAggregateAnnotationTestCase.test_annotation_exists_none_query",
+            "lookup.tests.LookupTests.test_exact_exists",
+            "lookup.tests.LookupTests.test_nested_outerref_lhs",
+            "lookup.tests.LookupQueryingTests.test_filter_exists_lhs",
+        },
+        "Subquery is not supported on MongoDB.": {
+            "annotations.tests.NonAggregateAnnotationTestCase.test_empty_queryset_annotation",
+            "db_functions.datetime.test_extract_trunc.DateFunctionTests.test_extract_outerref",
+            "db_functions.datetime.test_extract_trunc.DateFunctionTests.test_trunc_subquery_with_parameters",
+            "lookup.tests.LookupQueryingTests.test_filter_subquery_lhs",
+            "model_fields.test_jsonfield.TestQuerying.test_nested_key_transform_on_subquery",
+            "model_fields.test_jsonfield.TestQuerying.test_obj_subquery_lookup",
+        },
+        "Using a QuerySet in annotate() is not supported on MongoDB.": {
+            "annotations.tests.NonAggregateAnnotationTestCase.test_annotation_and_alias_filter_in_subquery",
+            "annotations.tests.NonAggregateAnnotationTestCase.test_empty_expression_annotation",
+            "db_functions.comparison.test_coalesce.CoalesceTests.test_empty_queryset",
+            "expressions_case.tests.CaseExpressionTests.test_in_subquery",
+            "lookup.tests.LookupTests.test_in_different_database",
+            "model_fields.test_jsonfield.TestQuerying.test_usage_in_subquery",
+        },
         "Count doesn't work in QuerySet.annotate()": {
             "annotations.tests.AliasTests.test_alias_annotate_with_aggregation",
             "annotations.tests.AliasTests.test_order_by_alias_aggregate",