diff --git a/mujoco_warp/_src/io.py b/mujoco_warp/_src/io.py
index a8c00483f..fa98a6f54 100644
--- a/mujoco_warp/_src/io.py
+++ b/mujoco_warp/_src/io.py
@@ -2176,6 +2176,28 @@ def get_data_into(
     # TODO(team): if sparse, set nJ based on sparse efc_J
     mujoco._functions._realloc_con_efc(result, ncon=ncon, nefc=nefc, nJ=nefc * mjm.nv)
 
+  # Check island compatibility between MjModel and Data
+  mjm_islands_enabled = not bool(mjm.opt.disableflags & mujoco.mjtDisableBit.mjDSBL_ISLAND)
+
+  # Check if device island arrays are allocated (automatically enabled when sleep is enabled).
+  # TODO(team): update when islands are enabled by default.
+  d_islands_enabled = d.tree_island.shape[1] > 0
+
+  if mjm_islands_enabled != d_islands_enabled:
+    raise ValueError("MjModel and Data island configurations do not match.")
+
+  # Reallocate host island fields if islands/sleep are enabled in host model options.
+  host_islands_allocated = mjm_islands_enabled and (
+    bool(mjm.opt.enableflags & mujoco.mjtEnableBit.mjENBL_SLEEP)
+    or bool(mjm.opt.enableflags & getattr(mujoco.mjtEnableBit, "mjENBL_ISLAND", 0))
+  )
+
+  if host_islands_allocated:
+    nisland = d.nisland.numpy()[world_id]
+    nidof = d.nidof.numpy()[world_id]
+    if result.island_idofadr.shape[0] < nisland or result.dof_island.shape[0] < nidof:
+      mujoco._functions._realloc_island(result, nisland=nisland, nidof=nidof)
+
   ne = d.ne.numpy()[world_id]
   nf = d.nf.numpy()[world_id]
   nl = d.nl.numpy()[world_id]
@@ -2370,23 +2392,29 @@ def get_data_into(
   result.body_awake[:] = d.body_awake.numpy()[world_id]
 
   # islands
-  nisland = d.nisland.numpy()[world_id]
-  result.nisland = nisland
-  if d.tree_island.shape[1] > 0 and nisland:
-    result.tree_island[:] = d.tree_island.numpy()[world_id]
-    result.dof_island[:] = d.dof_island.numpy()[world_id]
-    result.island_idofadr[:nisland] = d.island_idofadr.numpy()[world_id, :nisland]
-    result.island_dofadr[:nisland] = d.island_dofadr.numpy()[world_id, :nisland]
-    result.island_nv[:nisland] = d.island_nv.numpy()[world_id, :nisland]
-    result.island_nefc[:nisland] = d.island_nefc.numpy()[world_id, :nisland]
-    result.island_ne[:nisland] = d.island_ne.numpy()[world_id, :nisland]
-    result.island_nf[:nisland] = d.island_nf.numpy()[world_id, :nisland]
-    result.island_iefcadr[:nisland] = d.island_iefcadr.numpy()[world_id, :nisland]
-    nv = mjm.nv
-    result.map_dof2idof[:nv] = d.map_dof2idof.numpy()[world_id, :nv]
-    result.map_idof2dof[:nv] = d.map_idof2dof.numpy()[world_id, :nv]
-    result.map_efc2iefc[:nefc] = d.map_efc2iefc.numpy()[world_id, :nefc]
-    result.map_iefc2efc[:nefc] = d.map_iefc2efc.numpy()[world_id, :nefc]
+  if mjm_islands_enabled and d.tree_island.shape[1] > 0:
+    nisland = d.nisland.numpy()[world_id]
+    result.nisland = nisland
+    if nisland > 0:
+      result.tree_island[:] = d.tree_island.numpy()[world_id]
+      result.dof_island[:] = d.dof_island.numpy()[world_id]
+      if result.island_idofadr.shape[0] >= nisland:
+        result.island_idofadr[:nisland] = d.island_idofadr.numpy()[world_id, :nisland]
+        result.island_dofadr[:nisland] = d.island_dofadr.numpy()[world_id, :nisland]
+        result.island_nv[:nisland] = d.island_nv.numpy()[world_id, :nisland]
+        result.island_nefc[:nisland] = d.island_nefc.numpy()[world_id, :nisland]
+        result.island_ne[:nisland] = d.island_ne.numpy()[world_id, :nisland]
+        result.island_nf[:nisland] = d.island_nf.numpy()[world_id, :nisland]
+        result.island_iefcadr[:nisland] = d.island_iefcadr.numpy()[world_id, :nisland]
+      nv = mjm.nv
+      if result.map_dof2idof.shape[0] >= nv:
+        result.map_dof2idof[:nv] = d.map_dof2idof.numpy()[world_id, :nv]
+        result.map_idof2dof[:nv] = d.map_idof2dof.numpy()[world_id, :nv]
+      if result.map_efc2iefc.shape[0] >= nefc:
+        result.map_efc2iefc[:nefc] = d.map_efc2iefc.numpy()[world_id, :nefc]
+        result.map_iefc2efc[:nefc] = d.map_iefc2efc.numpy()[world_id, :nefc]
+  else:
+    result.nisland = 0
 
 
 def reset_data(m: types.Model, d: types.Data, reset: Optional[wp.array] = None):
diff --git a/mujoco_warp/_src/io_test.py b/mujoco_warp/_src/io_test.py
index 58ed68145..7cfdbfa3f 100644
--- a/mujoco_warp/_src/io_test.py
+++ b/mujoco_warp/_src/io_test.py
@@ -747,6 +747,63 @@ def test_get_data_into(self, nworld, world_id):
         field,
       )
 
+  def test_get_data_into_realloc_island(self):
+    mjm, mjd, m, d = test_data.fixture(
+      xml="""
+    <mujoco>
+      <option>
+        <flag sleep="enable"/>
+      </option>
+      <size memory="100M"/>
+      <worldbody>
+        <body>
+          <joint type="free"/>
+          <geom type="sphere" size="0.1"/>
+        </body>
+        <body>
+          <joint type="free"/>
+          <geom type="sphere" size="0.1"/>
+        </body>
+      </worldbody>
+    </mujoco>
+    """,
+      nworld=1,
+    )
+
+    expected_nisland = int(d.nisland.numpy()[0])
+    expected_nidof = int(d.nidof.numpy()[0])
+
+    mjwarp.get_data_into(mjd, mjm, d, world_id=0)
+
+    self.assertEqual(mjd.nisland, expected_nisland)
+    self.assertEqual(mjd.island_idofadr.shape[0], expected_nisland)
+
+  def test_get_data_into_islands_disabled_error(self):
+    mjm, mjd, m, d = test_data.fixture(
+      xml="""
+    <mujoco>
+      <option>
+        <flag island="disable"/>
+      </option>
+      <worldbody>
+        <body>
+          <joint type="free"/>
+          <geom type="sphere" size="0.1"/>
+        </body>
+        <body>
+          <joint type="free"/>
+          <geom type="sphere" size="0.1"/>
+        </body>
+      </worldbody>
+    </mujoco>
+    """,
+      nworld=1,
+    )
+    mjwarp.forward(m, d)
+    if d.nisland.numpy()[0] > 0:
+      with self.assertRaisesRegex(ValueError, "islands are disabled in MjModel"):
+        mjwarp.get_data_into(mjd, mjm, d, world_id=0)
+
   @parameterized.product(
     xml=_IO_TEST_MODELS,
     cone=list(ConeType),