diff --git a/dcargs/_parsers.py b/dcargs/_parsers.py
index 46d6965c..815bd187 100644
--- a/dcargs/_parsers.py
+++ b/dcargs/_parsers.py
@@ -255,8 +255,8 @@ def from_field(
         # Add subparser for each option.
         parser_from_name: Dict[str, ParserSpecification] = {}
         for option in options_no_none:
-            subparser_name = _strings.subparser_name_from_type(prefix, option)
-            parser_from_name[subparser_name] = ParserSpecification.from_callable(
+            name = _strings.subparser_name_from_type(prefix, option)
+            subparser = ParserSpecification.from_callable(
                 option,
                 description=None,
                 parent_classes=parent_classes,
@@ -268,6 +268,16 @@ def from_field(
                 avoid_subparsers=avoid_subparsers,
             )
 
+            # Apply prefix to helptext in nested classes in subparsers.
+            subparser = dataclasses.replace(
+                subparser,
+                helptext_from_nested_class_field_name={
+                    _strings.make_field_name([prefix, k]): v
+                    for k, v in subparser.helptext_from_nested_class_field_name.items()
+                },
+            )
+            parser_from_name[name] = subparser
+
         # Optional if: type hint is Optional[], or a default instance is provided.
         required = True
         if field.default not in _fields.MISSING_SINGLETONS:
diff --git a/pyproject.toml b/pyproject.toml
index cda21fa8..bd329a31 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "dcargs"
-version = "0.2.7"
+version = "0.2.8"
 description = "Strongly typed, zero-effort CLI interfaces"
 authors = ["brentyi <brentyi@berkeley.edu>"]
 include = ["./dcargs/**/*"]
diff --git a/tests/test_nested.py b/tests/test_nested.py
index eae4840d..b52f25be 100644
--- a/tests/test_nested.py
+++ b/tests/test_nested.py
@@ -745,3 +745,30 @@ def main(
     assert hash(dcargs.cli(main, args="--x.num-epochs 10".split(" "))) == hash(
         frozendict({"num_epochs": 10, "batch_size": 64})
     )
+
+
+def test_nested_in_subparser():
+    # https://github.com/brentyi/dcargs/issues/9
+    @dataclasses.dataclass(frozen=True)
+    class Subtype:
+        data: int = 1
+
+    @dataclasses.dataclass(frozen=True)
+    class TypeA:
+        subtype: Subtype = Subtype(1)
+
+    @dataclasses.dataclass(frozen=True)
+    class TypeB:
+        subtype: Subtype = Subtype(2)
+
+    @dataclasses.dataclass(frozen=True)
+    class Wrapper:
+        supertype: Union[TypeA, TypeB] = TypeA()
+
+    assert dcargs.cli(Wrapper, args=[]) == Wrapper()
+    assert (
+        dcargs.cli(
+            Wrapper, args="supertype:type-a --supertype.subtype.data 1".split(" ")
+        )
+        == Wrapper()
+    )