diff --git a/homeassistant/components/knx/icons.json b/homeassistant/components/knx/icons.json
index e13a41ba3c2f..09a6c5b89772 100644
--- a/homeassistant/components/knx/icons.json
+++ b/homeassistant/components/knx/icons.json
@@ -21,6 +21,9 @@
       "telegram_count": {
         "default": "mdi:plus-network"
       },
+      "telegrams_data_secure_undecodable": {
+        "default": "mdi:lock-alert"
+      },
       "telegrams_incoming": {
         "default": "mdi:upload-network"
       },
diff --git a/homeassistant/components/knx/sensor.py b/homeassistant/components/knx/sensor.py
index 2a3732e7fcdb..480f7d68db2e 100644
--- a/homeassistant/components/knx/sensor.py
+++ b/homeassistant/components/knx/sensor.py
@@ -108,6 +108,12 @@ SYSTEM_ENTITY_DESCRIPTIONS = (
         + knx.xknx.connection_manager.cemi_count_incoming
         + knx.xknx.connection_manager.cemi_count_incoming_error,
     ),
+    KNXSystemEntityDescription(
+        key="telegrams_data_secure_undecodable",
+        entity_registry_enabled_default=False,
+        state_class=SensorStateClass.TOTAL_INCREASING,
+        value_fn=lambda knx: knx.xknx.connection_manager.undecoded_data_secure,
+    ),
 )
 
 
diff --git a/homeassistant/components/knx/strings.json b/homeassistant/components/knx/strings.json
index 6c61a737570f..3d5e88420a7c 100644
--- a/homeassistant/components/knx/strings.json
+++ b/homeassistant/components/knx/strings.json
@@ -639,6 +639,10 @@
         "name": "Telegrams",
         "unit_of_measurement": "telegrams"
       },
+      "telegrams_data_secure_undecodable": {
+        "name": "Undecodable Data Secure telegrams",
+        "unit_of_measurement": "[%key:component::knx::entity::sensor::telegrams_incoming_error::unit_of_measurement%]"
+      },
       "telegrams_incoming": {
         "name": "Incoming telegrams",
         "unit_of_measurement": "[%key:component::knx::entity::sensor::telegram_count::unit_of_measurement%]"
diff --git a/tests/components/knx/test_interface_device.py b/tests/components/knx/test_interface_device.py
index 4de366c69f03..0d804deb333e 100644
--- a/tests/components/knx/test_interface_device.py
+++ b/tests/components/knx/test_interface_device.py
@@ -36,6 +36,7 @@ async def test_diagnostic_entities(
         "sensor.knx_interface_outgoing_telegrams",
         "sensor.knx_interface_outgoing_telegram_errors",
         "sensor.knx_interface_telegrams",
+        "sensor.knx_interface_undecodable_data_secure_telegrams",
     ):
         entity = entity_registry.async_get(entity_id)
         assert entity.entity_category is EntityCategory.DIAGNOSTIC
@@ -43,6 +44,7 @@ async def test_diagnostic_entities(
     for entity_id in (
         "sensor.knx_interface_incoming_telegrams",
         "sensor.knx_interface_outgoing_telegrams",
+        "sensor.knx_interface_undecodable_data_secure_telegrams",
     ):
         entity = entity_registry.async_get(entity_id)
         assert entity.disabled is True
@@ -57,7 +59,7 @@ async def test_diagnostic_entities(
     async_fire_time_changed(hass)
     await hass.async_block_till_done()
 
-    assert len(events) == 3  # 5 polled sensors - 2 disabled
+    assert len(events) == 3  # 6 polled sensors - 3 disabled
     events.clear()
 
     for entity_id, test_state in (
@@ -74,7 +76,7 @@ async def test_diagnostic_entities(
         state=XknxConnectionState.DISCONNECTED
     )
     await hass.async_block_till_done()
-    assert len(events) == 4  # 3 not always_available + 3 force_update - 2 disabled
+    assert len(events) == 4
     events.clear()
 
     knx.xknx.current_address = IndividualAddress("1.1.1")