diff --git a/blueprintcompiler/language/expression.py b/blueprintcompiler/language/expression.py
index 558392c..ae9c399 100644
--- a/blueprintcompiler/language/expression.py
+++ b/blueprintcompiler/language/expression.py
@@ -171,6 +171,24 @@ class LookupOp(InfixExpr):
                 did_you_mean=(self.property_name, self.lhs.type.properties.keys()),
             )
 
+    @validate("property")
+    def property_deprecated(self):
+        if self.lhs.type is None or not (
+            isinstance(self.lhs.type, gir.Class)
+            or isinstance(self.lhs.type, gir.Interface)
+        ):
+            return
+
+        if property := self.lhs.type.properties.get(self.property_name):
+            if property.deprecated:
+                hints = []
+                if property.deprecated_doc:
+                    hints.append(property.deprecated_doc)
+                raise DeprecatedWarning(
+                    f"{property.signature} is deprecated",
+                    hints=hints,
+                )
+
 
 class CastExpr(InfixExpr):
     grammar = [
diff --git a/tests/sample_errors/deprecations.blp b/tests/sample_errors/deprecations.blp
deleted file mode 100644
index f67f002..0000000
--- a/tests/sample_errors/deprecations.blp
+++ /dev/null
@@ -1,9 +0,0 @@
-using Gtk 4.0;
-
-Dialog {
-  use-header-bar: 1;
-}
-
-Window {
-  keys-changed => $on_window_keys_changed();
-}
diff --git a/tests/sample_errors/deprecations.err b/tests/sample_errors/deprecations.err
deleted file mode 100644
index e3abd61..0000000
--- a/tests/sample_errors/deprecations.err
+++ /dev/null
@@ -1 +0,0 @@
-3,1,6,Gtk.Dialog is deprecated
\ No newline at end of file
diff --git a/tests/test_deprecations.py b/tests/test_deprecations.py
new file mode 100644
index 0000000..0ffe726
--- /dev/null
+++ b/tests/test_deprecations.py
@@ -0,0 +1,110 @@
+# test_samples.py
+#
+# Copyright 2024 James Westman <james@jwestman.net>
+#
+# This file is free software; you can redistribute it and/or modify it
+# under the terms of the GNU Lesser General Public License as
+# published by the Free Software Foundation; either version 3 of the
+# License, or (at your option) any later version.
+#
+# This file is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+# SPDX-License-Identifier: LGPL-3.0-or-later
+
+
+import unittest
+
+import gi
+
+gi.require_version("Gtk", "4.0")
+from gi.repository import Gtk
+
+from blueprintcompiler import parser, tokenizer
+from blueprintcompiler.errors import DeprecatedWarning, PrintableError
+
+# Testing deprecation warnings requires special handling because libraries can add deprecations with new versions,
+# causing tests to break if we're not careful.
+
+
+class TestDeprecations(unittest.TestCase):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+        self.gtkVersion = f"{Gtk.get_major_version()}.{Gtk.get_minor_version()}.{Gtk.get_micro_version()}"
+
+    def assertDeprecation(self, blueprint: str, message: str):
+        try:
+            tokens = tokenizer.tokenize(blueprint)
+            _ast, errors, warnings = parser.parse(tokens)
+
+            self.assertIsNone(errors)
+            self.assertEqual(len(warnings), 1)
+            self.assertIsInstance(warnings[0], DeprecatedWarning)
+            self.assertEqual(warnings[0].message, message)
+        except PrintableError as e:  # pragma: no cover
+            e.pretty_print("<deprecations test>", blueprint)
+            raise AssertionError()
+
+    def test_class_deprecation(self):
+        if Gtk.check_version(4, 10, 0) is not None:
+            self.skipTest(f"Gtk.Dialog is not deprecated in GTK {self.gtkVersion}")
+
+        blueprint = """
+        using Gtk 4.0;
+
+        Dialog {
+            use-header-bar: 1;
+        }
+        """
+        message = "Gtk.Dialog is deprecated"
+
+        self.assertDeprecation(blueprint, message)
+
+    def test_property_deprecation(self):
+        self.skipTest(
+            "gobject-introspection does not currently write property deprecations to the typelib. See <https://gitlab.gnome.org/GNOME/gobject-introspection/-/merge_requests/410>."
+        )
+
+        if Gtk.check_version(4, 4, 0) is not None:
+            self.skipTest(
+                f"Gtk.DropTarget:drop is not deprecated in GTK {self.gtkVersion}"
+            )
+
+        blueprint = """
+        using Gtk 4.0;
+
+        $MyObject {
+            a: bind drop_target.drop;
+        }
+
+        DropTarget drop_target {
+        }
+        """
+
+        message = "Gtk.DropTarget:drop is deprecated"
+
+        self.assertDeprecation(blueprint, message)
+
+    def test_signal_deprecation(self):
+        if Gtk.check_version(4, 10, 0) is not None:
+            self.skipTest(
+                f"Gtk.Window::keys-changed is not deprecated in GTK {self.gtkVersion}"
+            )
+
+        blueprint = """
+        using Gtk 4.0;
+
+        Window {
+            keys-changed => $handler();
+        }
+        """
+
+        message = "signal Gtk.Window::keys-changed () is deprecated"
+
+        self.assertDeprecation(blueprint, message)