diff --git a/geopandas/geodataframe.py b/geopandas/geodataframe.py
index 3091e52..cd9c475 100644
--- a/geopandas/geodataframe.py
+++ b/geopandas/geodataframe.py
@@ -68,7 +68,7 @@ class GeoDataFrame(DataFrame):
 
     def set_geometry(self, col, drop=False, inplace=False, crs=None):
         """
-        Set the GeoDataFrame geometry using either an existing column or 
+        Set the GeoDataFrame geometry using either an existing column or
         the specified input. By default yields a new object.
 
         The original geometry column is replaced with the input.
@@ -80,6 +80,10 @@ class GeoDataFrame(DataFrame):
             Delete column to be used as the new geometry
         inplace : boolean, default False
             Modify the GeoDataFrame in place (do not create a new object)
+        crs : str/result of fion.get_crs (optional)
+            Coordinate system to use. If passed, overrides both DataFrame and
+            col's crs. Otherwise, tries to get crs from passed col values or
+            DataFrame.
 
         Examples
         --------
@@ -96,7 +100,8 @@ class GeoDataFrame(DataFrame):
         else:
             frame = self.copy()
 
-        crs = crs or self.crs
+        if not crs:
+            crs = getattr(col, 'crs', self.crs)
 
         to_remove = None
         geo_column_name = DEFAULT_GEO_COLUMN_NAME
@@ -122,6 +127,11 @@ class GeoDataFrame(DataFrame):
         if to_remove:
             del frame[to_remove]
 
+        if isinstance(level, GeoSeries) and level.crs != crs:
+            # avoids caching issues/crs sharing issues
+            level = level.copy()
+            level.crs = crs
+
         frame[geo_column_name] = level
         frame._geometry_column_name = geo_column_name
         frame.crs = crs
diff --git a/tests/test_geodataframe.py b/tests/test_geodataframe.py
index 8e4486e..bacbc55 100644
--- a/tests/test_geodataframe.py
+++ b/tests/test_geodataframe.py
@@ -73,6 +73,11 @@ class TestDataFrame(unittest.TestCase):
         tu.assert_geoseries_equal(df.geometry, new_geom)
         tu.assert_geoseries_equal(df['geometry'], new_geom)
 
+        # new crs
+        gs = GeoSeries(new_geom, crs="epsg:26018")
+        df.geometry = gs
+        self.assertEqual(df.crs, "epsg:26018")
+
     def test_geometry_property_errors(self):
         # TODO: Much cleaner if we use pandas test options (since assertRaises
         # contextmanager and friends not available in 2.6), but need 0.13 for
@@ -124,6 +129,21 @@ class TestDataFrame(unittest.TestCase):
         self.assertRaises(ValueError, self.df.set_geometry,
                           self.df)
 
+        # new crs - setting should default to GeoSeries' crs
+        gs = GeoSeries(geom, crs="epsg:26018")
+        new_df = self.df.set_geometry(gs)
+        self.assertEqual(new_df.crs, "epsg:26018")
+
+        # explicit crs overrides self and dataframe
+        new_df = self.df.set_geometry(gs, crs="epsg:27159")
+        self.assertEqual(new_df.crs, "epsg:27159")
+        self.assertEqual(new_df.geometry.crs, "epsg:27159")
+
+        # Series should use dataframe's
+        new_df = self.df.set_geometry(geom.values)
+        self.assertEqual(new_df.crs, self.df.crs)
+        self.assertEqual(new_df.geometry.crs, self.df.crs)
+
     def test_set_geometry_col(self):
         g = self.df.geometry
         g_simplified = g.simplify(100)