diff --git a/doc/source/whatsnew/v0.25.1.rst b/doc/source/whatsnew/v0.25.1.rst
index fb67decb46b64..40fefe7ec43a8 100644
--- a/doc/source/whatsnew/v0.25.1.rst
+++ b/doc/source/whatsnew/v0.25.1.rst
@@ -78,7 +78,7 @@ Strings
 
 Interval
 ^^^^^^^^
-
+- Bug in :class:`IntervalIndex` where `dir(obj)` would raise ``ValueError`` (:issue:`27571`)
 -
 -
 -
diff --git a/pandas/_libs/lib.pyx b/pandas/_libs/lib.pyx
index 928af2de03b5f..47d1e98f214a1 100644
--- a/pandas/_libs/lib.pyx
+++ b/pandas/_libs/lib.pyx
@@ -925,6 +925,7 @@ _TYPE_MAP = {
     'M': 'datetime64',
     'timedelta64[ns]': 'timedelta64',
     'm': 'timedelta64',
+    'interval': 'interval',
 }
 
 # types only exist on certain platform
diff --git a/pandas/core/strings.py b/pandas/core/strings.py
index 8f06470db60f1..169a3a24c254d 100644
--- a/pandas/core/strings.py
+++ b/pandas/core/strings.py
@@ -1961,8 +1961,11 @@ def _validate(data):
         values = getattr(data, "values", data)  # Series / Index
         values = getattr(values, "categories", values)  # categorical / normal
 
-        # missing values obfuscate type inference -> skip
-        inferred_dtype = lib.infer_dtype(values, skipna=True)
+        try:
+            inferred_dtype = lib.infer_dtype(values, skipna=True)
+        except ValueError:
+            # GH#27571 mostly occurs with ExtensionArray
+            inferred_dtype = None
 
         if inferred_dtype not in allowed_types:
             raise AttributeError("Can only use .str accessor with string values!")
diff --git a/pandas/tests/dtypes/test_inference.py b/pandas/tests/dtypes/test_inference.py
index 0ae4fcc0fef83..0a8707bdac3a0 100644
--- a/pandas/tests/dtypes/test_inference.py
+++ b/pandas/tests/dtypes/test_inference.py
@@ -1168,6 +1168,17 @@ def test_categorical(self):
         result = lib.infer_dtype(Series(arr), skipna=True)
         assert result == "categorical"
 
+    def test_interval(self):
+        idx = pd.IntervalIndex.from_breaks(range(5), closed="both")
+        inferred = lib.infer_dtype(idx, skipna=False)
+        assert inferred == "interval"
+
+        inferred = lib.infer_dtype(idx._data, skipna=False)
+        assert inferred == "interval"
+
+        inferred = lib.infer_dtype(pd.Series(idx), skipna=False)
+        assert inferred == "interval"
+
 
 class TestNumberScalar:
     def test_is_number(self):
diff --git a/pandas/tests/indexes/interval/test_interval.py b/pandas/tests/indexes/interval/test_interval.py
index c61af1ce70aed..c1a21e6a7f152 100644
--- a/pandas/tests/indexes/interval/test_interval.py
+++ b/pandas/tests/indexes/interval/test_interval.py
@@ -1095,3 +1095,10 @@ def test_is_all_dates(self):
         )
         year_2017_index = pd.IntervalIndex([year_2017])
         assert not year_2017_index.is_all_dates
+
+
+def test_dir():
+    # GH#27571 dir(interval_index) should not raise
+    index = IntervalIndex.from_arrays([0, 1], [1, 2])
+    result = dir(index)
+    assert "str" not in result