@@ -144,7 +144,7 @@ Numeric
 
 Conversion
 ^^^^^^^^^^
--
+- Bug in :meth:`ArrowDtype.numpy_dtype` returning nanosecond units for non-nanosecond ``pyarrow.timestamp`` and ``pyarrow.duration`` types (:issue:`51800`)
 -
 
 Strings

@@ -148,6 +148,18 @@ def name(self) -> str: # type: ignore[override]
 @cache_readonly
 def numpy_dtype(self) -> np.dtype:
 """Return an instance of the related numpy dtype"""
+if pa.types.is_timestamp(self.pyarrow_dtype):
+# pa.timestamp(unit).to_pandas_dtype() returns ns units
+# regardless of the pyarrow timestamp units.
+# This can be removed if/when pyarrow addresses it:
+# https://.com/apache/arrow/issues/34462
+return np.dtype(f"datetime64[{self.pyarrow_dtype.unit}]")
+if pa.types.is_duration(self.pyarrow_dtype):
+# pa.duration(unit).to_pandas_dtype() returns ns units
+# regardless of the pyarrow duration units
+# This can be removed if/when pyarrow addresses it:
+# https://.com/apache/arrow/issues/34462
+return np.dtype(f"timedelta64[{self.pyarrow_dtype.unit}]")
 if pa.types.is_string(self.pyarrow_dtype):
 # pa.string().to_pandas_dtype() = object which we don't want
 return np.dtype(str)

@@ -640,11 +640,7 @@ def test_get_common_dtype(self, dtype, request):
 if (
 pa.types.is_date(pa_dtype)
 or pa.types.is_time(pa_dtype)
-or (
-pa.types.is_timestamp(pa_dtype)
-and (pa_dtype.unit != "ns" or pa_dtype.tz is not None)
-)
-or (pa.types.is_duration(pa_dtype) and pa_dtype.unit != "ns")
+or (pa.types.is_timestamp(pa_dtype) and pa_dtype.tz is not None)
 or pa.types.is_binary(pa_dtype)
 or pa.types.is_decimal(pa_dtype)
 ):