diff --git a/loki/ir/nodes.py b/loki/ir/nodes.py
index 6599df90b..56ae34e7b 100644
--- a/loki/ir/nodes.py
+++ b/loki/ir/nodes.py
@@ -879,6 +879,23 @@ class CallStatement(LeafNode, _CallStatementBase):
 
     _traversable = ['name', 'arguments', 'kwarguments']
 
+    @model_validator(mode='before')
+    @classmethod
+    def pre_init(cls, values):
+        # Ensure non-nested tuples for arguments
+        if 'arguments' in values.kwargs:
+            values.kwargs['arguments'] = _sanitize_tuple(values.kwargs['arguments'])
+        else:
+            values.kwargs['arguments'] = ()
+        # Ensure two-level nested tuples for kwarguments
+        if 'kwarguments' in values.kwargs:
+            kwarguments = as_tuple(values.kwargs['kwarguments'])
+            kwarguments = tuple(_sanitize_tuple(pair) for pair in kwarguments)
+            values.kwargs['kwarguments'] = kwarguments
+        else:
+            values.kwargs['kwarguments'] = ()
+        return values
+
     def __post_init__(self):
         super().__post_init__()
         assert isinstance(self.arguments, tuple)
diff --git a/loki/ir/tests/test_ir_nodes.py b/loki/ir/tests/test_ir_nodes.py
index cb17ea943..97a410c6b 100644
--- a/loki/ir/tests/test_ir_nodes.py
+++ b/loki/ir/tests/test_ir_nodes.py
@@ -196,3 +196,51 @@ def test_section(scope, one, i, n, a_n, a_i):
     assert sec.body == (assign, func, assign, assign)
     sec.insert(pos=3, node=func)
     assert sec.body == (assign, func, assign, func, assign)
+
+
+def test_callstatement(scope, one, i, n, a_i):
+    """ Test constructor of :any:`CallStatement` nodes. """
+
+    cname = sym.ProcedureSymbol(name='test', scope=scope)
+    call = ir.CallStatement(
+        name=cname, arguments=(n, a_i), kwarguments=(('i', i), ('j', one))
+    )
+    assert isinstance(call.name, Expression)
+    assert isinstance(call.arguments, tuple)
+    assert all(isinstance(e, Expression) for e in call.arguments)
+    assert isinstance(call.kwarguments, tuple)
+    assert all(isinstance(e, tuple) for e in call.kwarguments)
+    assert all(
+        isinstance(k, str) and isinstance(v, Expression)
+        for k, v in call.kwarguments
+    )
+
+    # Ensure "frozen" status of node objects
+    with pytest.raises(FrozenInstanceError) as error:
+        call.name = sym.ProcedureSymbol('dave', scope=scope)
+    with pytest.raises(FrozenInstanceError) as error:
+        call.arguments = (a_i, n, one)
+    with pytest.raises(FrozenInstanceError) as error:
+        call.kwarguments = (('i', one), ('j', i))
+
+    # Test auto-casting of the body to tuple
+    call = ir.CallStatement(name=cname, arguments=[a_i, one])
+    assert call.arguments == (a_i, one) and call.kwarguments == ()
+    call = ir.CallStatement(name=cname, arguments=None)
+    assert call.arguments == () and call.kwarguments == ()
+    call = ir.CallStatement(name=cname, kwarguments=[('i', i), ('j', one)])
+    assert call.arguments == () and call.kwarguments == (('i', i), ('j', one))
+    call = ir.CallStatement(name=cname, kwarguments=None)
+    assert call.arguments == () and call.kwarguments == ()
+
+    # Test errors for wrong contructor usage
+    with pytest.raises(ValidationError) as error:
+        ir.CallStatement(name='a', arguments=(sym.Literal(42.0),))
+    with pytest.raises(ValidationError) as error:
+        ir.CallStatement(name=cname, arguments=('a',))
+    with pytest.raises(ValidationError) as error:
+        ir.Assignment(
+            name=cname, arguments=(sym.Literal(42.0),), kwarguments=('i', 'i')
+        )
+
+    # TODO: Test pragmas, active and chevron