diff --git a/examples/ui/file_browser.py b/examples/ui/file_browser.py
index 23961aec91d..5c1cc3bf580 100644
--- a/examples/ui/file_browser.py
+++ b/examples/ui/file_browser.py
@@ -24,5 +24,18 @@ def _(file_browser):
     return
 
 
+@app.cell
+def _(mo):
+    file_browser_all = mo.ui.file_browser(selection_mode="all")
+    file_browser_all
+    return (file_browser_all,)
+
+
+@app.cell
+def _(file_browser_all):
+    file_browser_all.value
+    return
+
+
 if __name__ == "__main__":
     app.run()
diff --git a/marimo/_plugins/ui/_impl/file_browser.py b/marimo/_plugins/ui/_impl/file_browser.py
index 5f7686abc67..602de44f07e 100644
--- a/marimo/_plugins/ui/_impl/file_browser.py
+++ b/marimo/_plugins/ui/_impl/file_browser.py
@@ -14,7 +14,6 @@
 from marimo import _loggers
 from marimo._output.rich_help import mddoc
 from marimo._plugins.ui._core.ui_element import UIElement
-from marimo._plugins.validators import validate_one_of
 from marimo._runtime.functions import Function
 from marimo._utils.files import natural_sort
 from marimo._utils.paths import is_cloudpath, normalize_path
@@ -22,6 +21,50 @@
 LOGGER = _loggers.marimo_logger()
 
 
+_VALID_KINDS: Final[frozenset[str]] = frozenset({"file", "directory"})
+
+
+def _normalize_selection_mode(
+    value: object,
+) -> frozenset[str]:
+    """Normalize ``selection_mode`` to a frozenset of selectable kinds.
+
+    Accepted inputs:
+        - ``"file"``      -> ``{"file"}``
+        - ``"directory"`` -> ``{"directory"}``
+        - ``"all"``       -> ``{"file", "directory"}``
+        - list/tuple containing ``"file"`` and/or ``"directory"`` (deduped)
+    """
+    if isinstance(value, str):
+        if value == "all":
+            return frozenset(_VALID_KINDS)
+        if value in _VALID_KINDS:
+            return frozenset({value})
+        raise ValueError(
+            f"Invalid selection_mode {value!r}. "
+            f"Expected one of 'file', 'directory', 'all', "
+            f"or a list of 'file'/'directory'."
+        )
+
+    if isinstance(value, (list, tuple)):
+        if len(value) == 0:
+            raise ValueError("selection_mode list must not be empty.")
+        kinds: set[str] = set()
+        for kind in value:
+            if not isinstance(kind, str) or kind not in _VALID_KINDS:
+                raise ValueError(
+                    f"Invalid selection_mode entry {kind!r}. "
+                    f"Each entry must be 'file' or 'directory'."
+                )
+            kinds.add(kind)
+        return frozenset(kinds)
+
+    raise ValueError(
+        f"selection_mode must be a string or a list of strings, "
+        f"got {type(value).__name__}."
+    )
+
+
 @dataclass
 class ListDirectoryArgs:
     path: str
@@ -70,6 +113,16 @@ class file_browser(
         file_browser.name(index=0)
         ```
 
+        Selecting both files and directories (useful for formats like
+        deltalake that are stored as directories):
+        ```python
+        file_browser = mo.ui.file_browser(
+            initial_path=Path("path/to/dir"),
+            selection_mode="all",
+            # Equivalent: selection_mode=["file", "directory"]
+        )
+        ```
+
         Connecting to an S3 (or GCS, Azure) bucket:
         ```python
         from cloudpathlib import S3Path
@@ -114,8 +167,10 @@ class file_browser(
         filetypes (Sequence[str], optional): The file types to display in each
             directory; for example, filetypes=[".txt", ".csv"]. If None, all
             files are displayed. Defaults to None.
-        selection_mode (Literal["file", "directory"], optional): Either "file" or "directory". Defaults to
-            "file".
+        selection_mode (str | Sequence[str], optional): Which kinds of entries
+            the user can select. Accepts one of "file" (default), "directory",
+            "all", or a list/tuple containing "file" and/or "directory".
+            "all" is equivalent to ["file", "directory"]. Defaults to "file".
         multiple (bool, optional): If True, allow the user to select multiple
             files. Defaults to True.
         restrict_navigation (bool, optional): If True, prevent the user from
@@ -140,7 +195,8 @@ def __init__(
         self,
         initial_path: str | Path = "",
         filetypes: Sequence[str] | None = None,
-        selection_mode: Literal["file", "directory"] = "file",
+        selection_mode: Literal["file", "directory", "all"]
+        | Sequence[Literal["file", "directory"]] = "file",
         multiple: bool = True,
         restrict_navigation: bool = False,
         *,
@@ -150,7 +206,7 @@ def __init__(
         | None = None,
         ignore_empty_dirs: bool = False,
     ) -> None:
-        validate_one_of(selection_mode, ["file", "directory"])
+        self._selection_mode = _normalize_selection_mode(selection_mode)
 
         # Save the Path class of the initial path
         self._path_cls: type[Path]
@@ -176,7 +232,6 @@ def __init__(
                 f"Initial path {initial_path} is not a directory."
             )
 
-        self._selection_mode = selection_mode
         # Normalize filetypes: ensure lowercase and dot prefix for case-insensitive matching
         if filetypes:
             normalized_filetypes = set()
@@ -201,13 +256,18 @@ def __init__(
 
         self._limit = limit
 
+        if self._selection_mode == _VALID_KINDS:
+            wire_selection_mode = "all"
+        else:
+            (wire_selection_mode,) = self._selection_mode
+
         super().__init__(
             component_name=file_browser._name,
             initial_value=[],
             label=label,
             args={
                 "initial-path": str(self._initial_path),
-                "selection-mode": selection_mode,
+                "selection-mode": wire_selection_mode,
                 "filetypes": filetypes if filetypes is not None else [],
                 "multiple": multiple,
                 "restrict-navigation": restrict_navigation,
@@ -316,8 +376,9 @@ def _list_directory(
             extension = file.suffix
             is_directory = file.is_dir()  # Expensive call for cloud paths
 
-            # Skip non-directories if selection mode is directory
-            if self._selection_mode == "directory" and not is_directory:
+            # Directories are always shown so the user can navigate into
+            # them. Files are hidden when files aren't selectable.
+            if not is_directory and "file" not in self._selection_mode:
                 continue
 
             # Skip non-matching file types (case-insensitive)
diff --git a/tests/_plugins/ui/_impl/test_file_browser.py b/tests/_plugins/ui/_impl/test_file_browser.py
index 8118d1825fd..92491486941 100644
--- a/tests/_plugins/ui/_impl/test_file_browser.py
+++ b/tests/_plugins/ui/_impl/test_file_browser.py
@@ -11,6 +11,7 @@
     FileBrowserFileInfo,
     ListDirectoryArgs,
     ListDirectoryResponse,
+    _normalize_selection_mode,
     file_browser,
 )
 from marimo._utils.paths import normalize_path
@@ -21,7 +22,7 @@ def test_file_browser_init(tmp_path: Path) -> None:
     fb = file_browser(initial_path=tmp_path)
     assert isinstance(fb._initial_path, Path)
     assert str(fb._initial_path) == str(normalize_path(tmp_path))
-    assert fb._selection_mode == "file"
+    assert fb._selection_mode == frozenset({"file"})
     assert fb._filetypes == set()
     assert fb._restrict_navigation is False
 
@@ -35,7 +36,7 @@ def test_file_browser_init(tmp_path: Path) -> None:
     )
     assert fb._initial_path == normalize_path(tmp_path)
     assert fb._filetypes == set(custom_filetypes)
-    assert fb._selection_mode == "directory"
+    assert fb._selection_mode == frozenset({"directory"})
     assert fb._restrict_navigation is True
 
 
@@ -352,8 +353,8 @@ def resolve(self) -> CustomPathWithClient:
 
 def test_validation() -> None:
     with pytest.raises(ValueError) as e:
-        file_browser(initial_path="invalid", selection_mode="invalid")
-    assert "Value must be one of" in str(e.value)
+        file_browser(initial_path="invalid", selection_mode="invalid")  # type: ignore[arg-type]
+    assert "Invalid selection_mode" in str(e.value)
 
 
 def test_limit_arg(tmp_path: Path) -> None:
@@ -1090,3 +1091,144 @@ def test_file_browser_relative_path_sent_to_frontend_as_absolute(
 
     finally:
         os.chdir(original_cwd)
+
+
+class TestNormalizeSelectionMode:
+    def test_string_file(self) -> None:
+        assert _normalize_selection_mode("file") == frozenset({"file"})
+
+    def test_string_directory(self) -> None:
+        assert _normalize_selection_mode("directory") == frozenset(
+            {"directory"}
+        )
+
+    def test_string_all(self) -> None:
+        assert _normalize_selection_mode("all") == frozenset(
+            {"file", "directory"}
+        )
+
+    def test_list_single_file(self) -> None:
+        assert _normalize_selection_mode(["file"]) == frozenset({"file"})
+
+    def test_list_single_directory(self) -> None:
+        assert _normalize_selection_mode(["directory"]) == frozenset(
+            {"directory"}
+        )
+
+    def test_list_both(self) -> None:
+        assert _normalize_selection_mode(["file", "directory"]) == frozenset(
+            {"file", "directory"}
+        )
+
+    def test_list_order_independent(self) -> None:
+        assert _normalize_selection_mode(["directory", "file"]) == frozenset(
+            {"file", "directory"}
+        )
+
+    def test_list_dedup(self) -> None:
+        assert _normalize_selection_mode(["file", "file"]) == frozenset(
+            {"file"}
+        )
+
+    def test_tuple_accepted(self) -> None:
+        assert _normalize_selection_mode(("file", "directory")) == frozenset(
+            {"file", "directory"}
+        )
+
+    @pytest.mark.parametrize(
+        "value",
+        [
+            "both",
+            "folder",
+            "",
+            "FILE",
+            [],
+            ["both"],
+            ["file", "nope"],
+            ["file", 1],
+            None,
+            123,
+        ],
+    )
+    def test_rejects_invalid(self, value: Any) -> None:
+        with pytest.raises(ValueError):
+            _normalize_selection_mode(value)
+
+
+class TestSelectionModeAll:
+    def test_init_all_string(self, tmp_path: Path) -> None:
+        fb = file_browser(initial_path=tmp_path, selection_mode="all")
+        assert fb._selection_mode == frozenset({"file", "directory"})
+
+    def test_init_list_form(self, tmp_path: Path) -> None:
+        fb = file_browser(
+            initial_path=tmp_path, selection_mode=["file", "directory"]
+        )
+        assert fb._selection_mode == frozenset({"file", "directory"})
+
+    def test_init_list_single(self, tmp_path: Path) -> None:
+        fb = file_browser(initial_path=tmp_path, selection_mode=["directory"])
+        assert fb._selection_mode == frozenset({"directory"})
+
+    def test_init_rejects_both(self, tmp_path: Path) -> None:
+        with pytest.raises(ValueError):
+            file_browser(initial_path=tmp_path, selection_mode="both")  # type: ignore[arg-type]
+
+    def test_init_rejects_empty_list(self, tmp_path: Path) -> None:
+        with pytest.raises(ValueError):
+            file_browser(initial_path=tmp_path, selection_mode=[])
+
+    def test_wire_format_all(self, tmp_path: Path) -> None:
+        fb = file_browser(initial_path=tmp_path, selection_mode="all")
+        assert fb._component_args["selection-mode"] == "all"
+
+    def test_wire_format_file(self, tmp_path: Path) -> None:
+        fb = file_browser(initial_path=tmp_path, selection_mode="file")
+        assert fb._component_args["selection-mode"] == "file"
+
+    def test_wire_format_directory(self, tmp_path: Path) -> None:
+        fb = file_browser(initial_path=tmp_path, selection_mode="directory")
+        assert fb._component_args["selection-mode"] == "directory"
+
+    def test_wire_format_list_normalized_to_all(self, tmp_path: Path) -> None:
+        fb = file_browser(
+            initial_path=tmp_path,
+            selection_mode=["directory", "file"],
+        )
+        assert fb._component_args["selection-mode"] == "all"
+
+    def test_list_directory_all_returns_files_and_dirs(
+        self, tmp_path: Path
+    ) -> None:
+        (tmp_path / "sub").mkdir()
+        (tmp_path / "a.txt").touch()
+        (tmp_path / "b.parquet").touch()
+        fb = file_browser(initial_path=tmp_path, selection_mode="all")
+        response = fb._list_directory(ListDirectoryArgs(path=str(tmp_path)))
+        names = {f["name"] for f in response.files}
+        assert names == {"sub", "a.txt", "b.parquet"}
+
+    def test_list_directory_all_respects_filetypes_for_files(
+        self, tmp_path: Path
+    ) -> None:
+        (tmp_path / "sub").mkdir()
+        (tmp_path / "a.txt").touch()
+        (tmp_path / "b.parquet").touch()
+        fb = file_browser(
+            initial_path=tmp_path,
+            selection_mode="all",
+            filetypes=[".parquet"],
+        )
+        response = fb._list_directory(ListDirectoryArgs(path=str(tmp_path)))
+        names = {f["name"] for f in response.files}
+        assert names == {"sub", "b.parquet"}
+
+    def test_list_directory_directory_only_unchanged(
+        self, tmp_path: Path
+    ) -> None:
+        (tmp_path / "sub").mkdir()
+        (tmp_path / "a.txt").touch()
+        fb = file_browser(initial_path=tmp_path, selection_mode="directory")
+        response = fb._list_directory(ListDirectoryArgs(path=str(tmp_path)))
+        names = {f["name"] for f in response.files}
+        assert names == {"sub"}