diff --git a/doc/source/whatsnew/v2.0.1.rst b/doc/source/whatsnew/v2.0.1.rst
index 0122c84ba2a8e..02fdff0e904eb 100644
--- a/doc/source/whatsnew/v2.0.1.rst
+++ b/doc/source/whatsnew/v2.0.1.rst
@@ -20,7 +20,7 @@ Fixed regressions
 
 Bug fixes
 ~~~~~~~~~
--
+- Bug in :class:`Series` constructor when passing ``timedelta64`` dtype with non-nanosecond unit would not respect the unit (:issue:`48312`, :issue:`52457`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_201.other:
diff --git a/pandas/core/arrays/timedeltas.py b/pandas/core/arrays/timedeltas.py
index 7731bb499cd21..237a5680eeab5 100644
--- a/pandas/core/arrays/timedeltas.py
+++ b/pandas/core/arrays/timedeltas.py
@@ -213,10 +213,12 @@ def _simple_new(  # type: ignore[override]
 
     @classmethod
     def _from_sequence(cls, data, *, dtype=None, copy: bool = False) -> Self:
+        unit = None
         if dtype:
             dtype = _validate_td64_dtype(dtype)
+            unit = np.datetime_data(dtype)[0]
 
-        data, inferred_freq = sequence_to_td64ns(data, copy=copy, unit=None)
+        data, inferred_freq = sequence_to_td64ns(data, copy=copy, unit=unit)
         freq, _ = dtl.validate_inferred_freq(None, inferred_freq, False)
         freq = cast("Tick | None", freq)
 
diff --git a/pandas/tests/indexing/test_scalar.py b/pandas/tests/indexing/test_scalar.py
index 1cb8c4f808fbd..57ee46d4d06f5 100644
--- a/pandas/tests/indexing/test_scalar.py
+++ b/pandas/tests/indexing/test_scalar.py
@@ -90,7 +90,10 @@ def test_at_iat_coercion(self):
                 Timestamp("2014-02-02"),
             ],
             [
-                Series(["1 days", "2 days"], dtype="timedelta64[ns]"),
+                Series(
+                    [86_400_000_000_000, 2 * 86_400_000_000_000],
+                    dtype="timedelta64[ns]",
+                ),
                 Timedelta("2 days"),
             ],
         ],
diff --git a/pandas/tests/series/test_constructors.py b/pandas/tests/series/test_constructors.py
index d3cc3239da482..a02efdfeccd46 100644
--- a/pandas/tests/series/test_constructors.py
+++ b/pandas/tests/series/test_constructors.py
@@ -52,14 +52,15 @@
 
 
 class TestSeriesConstructors:
-    def test_from_ints_with_non_nano_dt64_dtype(self, index_or_series):
+    @pytest.mark.parametrize("dtype", ["m8", "m8"])
+    def test_from_ints_with_non_nano_dt64_dtype(self, index_or_series, dtype):
         values = np.arange(10)
 
-        res = index_or_series(values, dtype="M8[s]")
-        expected = index_or_series(values.astype("M8[s]"))
+        res = index_or_series(values, dtype=f"{dtype}[s]")
+        expected = index_or_series(values.astype(f"{dtype}[s]"))
         tm.assert_equal(res, expected)
 
-        res = index_or_series(list(values), dtype="M8[s]")
+        res = index_or_series(list(values), dtype=f"{dtype}[s]")
         tm.assert_equal(res, expected)
 
     def test_from_na_value_and_interval_of_datetime_dtype(self):
@@ -1525,12 +1526,7 @@ def test_constructor_dtype_timedelta64(self):
             td.astype("int32")
 
         # this is an invalid casting
-        msg = "|".join(
-            [
-                "Could not convert object to NumPy timedelta",
-                "Could not convert 'foo' to NumPy timedelta",
-            ]
-        )
+        msg = "unit must not be specified if the input contains a str"
         with pytest.raises(ValueError, match=msg):
             Series([timedelta(days=1), "foo"], dtype="m8[ns]")
 
@@ -1958,21 +1954,6 @@ def test_constructor_dtype_timedelta_ns_s(self):
         expected = Series([1000000, 200000, 3000000], dtype="timedelta64[s]")
         tm.assert_series_equal(result, expected)
 
-    @pytest.mark.xfail(
-        reason="Not clear what the correct expected behavior should be with "
-        "integers now that we support non-nano. ATM (2022-10-08) we treat ints "
-        "as nanoseconds, then cast to the requested dtype. xref #48312"
-    )
-    def test_constructor_dtype_timedelta_ns_s_astype_int64(self):
-        # GH#35465
-        result = Series([1000000, 200000, 3000000], dtype="timedelta64[ns]").astype(
-            "int64"
-        )
-        expected = Series([1000000, 200000, 3000000], dtype="timedelta64[s]").astype(
-            "int64"
-        )
-        tm.assert_series_equal(result, expected)
-
     @pytest.mark.filterwarnings(
         "ignore:elementwise comparison failed:DeprecationWarning"
     )
@@ -2096,7 +2077,7 @@ def test_constructor_no_pandas_array(self, using_array_manager):
 
     @td.skip_array_manager_invalid_test
     def test_from_array(self):
-        result = Series(pd.array(["1H", "2H"], dtype="timedelta64[ns]"))
+        result = Series(pd.array([1, 2], dtype="timedelta64[ns]"))
         assert result._mgr.blocks[0].is_extension is False
 
         result = Series(pd.array(["2015"], dtype="datetime64[ns]"))
@@ -2104,7 +2085,7 @@ def test_from_array(self):
 
     @td.skip_array_manager_invalid_test
     def test_from_list_dtype(self):
-        result = Series(["1H", "2H"], dtype="timedelta64[ns]")
+        result = Series([1, 2], dtype="timedelta64[ns]")
         assert result._mgr.blocks[0].is_extension is False
 
         result = Series(["2015"], dtype="datetime64[ns]")