diff --git a/openmc/checkvalue.py b/openmc/checkvalue.py
index 840306486f..42df3e5efb 100644
--- a/openmc/checkvalue.py
+++ b/openmc/checkvalue.py
@@ -171,6 +171,29 @@ def check_length(name, value, length_min, length_max=None):
         raise ValueError(msg)
 
 
+def check_increasing(name: str, value, equality: bool = False):
+    """Ensure that a list's elements are strictly or loosely increasing.
+
+    Parameters
+    ----------
+    name : str
+        Description of value being checked
+    value : iterable
+        Object to check if increasing
+    equality : bool, optional
+        Whether equality is allowed. Defaults to False.
+
+    """
+    if equality:
+        if not np.all(np.diff(value) >= 0.0):
+            raise ValueError(f'Unable to set "{name}" to "{value}" since its '
+                             'elements must be increasing.')
+    elif not equality:
+        if not np.all(np.diff(value) > 0.0):
+            raise ValueError(f'Unable to set "{name}" to "{value}" since its '
+                             'elements must be strictly increasing.')
+
+
 def check_value(name, value, accepted_values):
     """Ensure that an object's value is contained in a set of acceptable values.
 
diff --git a/openmc/mesh.py b/openmc/mesh.py
index 8777da3255..48263c2055 100644
--- a/openmc/mesh.py
+++ b/openmc/mesh.py
@@ -1820,6 +1820,8 @@ class SphericalMesh(StructuredMesh):
     @r_grid.setter
     def r_grid(self, grid):
         cv.check_type('mesh r_grid', grid, Iterable, Real)
+        cv.check_length('mesh r_grid', grid, 2)
+        cv.check_increasing('mesh r_grid', grid)
         self._r_grid = np.asarray(grid, dtype=float)
 
     @property
@@ -1829,6 +1831,8 @@ class SphericalMesh(StructuredMesh):
     @theta_grid.setter
     def theta_grid(self, grid):
         cv.check_type('mesh theta_grid', grid, Iterable, Real)
+        cv.check_length('mesh theta_grid', grid, 2)
+        cv.check_increasing('mesh theta_grid', grid)
         self._theta_grid = np.asarray(grid, dtype=float)
 
     @property
@@ -1838,6 +1842,8 @@ class SphericalMesh(StructuredMesh):
     @phi_grid.setter
     def phi_grid(self, grid):
         cv.check_type('mesh phi_grid', grid, Iterable, Real)
+        cv.check_length('mesh phi_grid', grid, 2)
+        cv.check_increasing('mesh phi_grid', grid)
         self._phi_grid = np.asarray(grid, dtype=float)
 
     @property
diff --git a/tests/unit_tests/test_mesh.py b/tests/unit_tests/test_mesh.py
index c499306506..5bacd5fc69 100644
--- a/tests/unit_tests/test_mesh.py
+++ b/tests/unit_tests/test_mesh.py
@@ -132,6 +132,27 @@ def test_SphericalMesh_initiation():
     mesh.r_grid = (0, 11)
     assert (mesh.r_grid == np.array([0., 11.])).all()
 
+    # test invalid r_grid values
+    with pytest.raises(ValueError):
+        openmc.SphericalMesh(r_grid=[1, 1])
+
+    with pytest.raises(ValueError):
+        openmc.SphericalMesh(r_grid=[0])
+
+    # test invalid theta_grid values
+    with pytest.raises(ValueError):
+        openmc.SphericalMesh(r_grid=[1, 2], theta_grid=[1, 1])
+
+    with pytest.raises(ValueError):
+        openmc.SphericalMesh(r_grid=[1, 2], theta_grid=[0])
+
+    # test invalid phi_grid values
+    with pytest.raises(ValueError):
+        openmc.SphericalMesh(r_grid=[1, 2], phi_grid=[1, 1])
+
+    with pytest.raises(ValueError):
+        openmc.SphericalMesh(r_grid=[1, 2], phi_grid=[0])
+
     # waffles and pancakes are unfortunately not valid radii
     with pytest.raises(TypeError):
         openmc.SphericalMesh(('🧇', '🥞'))