diff --git a/homeassistant/components/sofar/diagnostics.py b/homeassistant/components/sofar/diagnostics.py
index 3ecea362805e..e421bc2e70ee 100644
--- a/homeassistant/components/sofar/diagnostics.py
+++ b/homeassistant/components/sofar/diagnostics.py
@@ -30,6 +30,7 @@ async def async_get_config_entry_diagnostics(
             "readings_components": device.readings_components,
             "settings_components": device.settings_components,
             "active_faults": sorted(fault.key for fault in device.state.active_faults),
+            "address_masks": await device.async_read_masks(),
             "raw": raw,
         },
         TO_REDACT,
diff --git a/tests/components/sofar/snapshots/test_diagnostics.ambr b/tests/components/sofar/snapshots/test_diagnostics.ambr
index a8e8adc7909e..339fda0b38f5 100644
--- a/tests/components/sofar/snapshots/test_diagnostics.ambr
+++ b/tests/components/sofar/snapshots/test_diagnostics.ambr
@@ -3,6 +3,22 @@
   dict({
     'active_faults': list([
     ]),
+    'address_masks': dict({
+      '1024': 0,
+      '1088': 0,
+      '1152': 0,
+      '1280': 0,
+      '1408': 0,
+      '1472': 0,
+      '1536': 0,
+      '1600': 0,
+      '1664': 0,
+      '1728': 0,
+      '4096': 0,
+      '4160': 0,
+      '4352': 0,
+      '4480': 0,
+    }),
     'inverter_type': 1537,
     'model': '4.4 KTLX-G3',
     'raw': dict({
diff --git a/tests/components/sofar/test_diagnostics.py b/tests/components/sofar/test_diagnostics.py
index d7aff386402c..e1a0d7588b16 100644
--- a/tests/components/sofar/test_diagnostics.py
+++ b/tests/components/sofar/test_diagnostics.py
@@ -60,3 +60,21 @@ async def test_diagnostics_redacts_serial_number(
     holding = diag["raw"]["holding"]
     for address in range(0x0445, 0x044C):
         assert str(address) not in holding
+
+
+async def test_diagnostics_decodes_address_masks(
+    hass: HomeAssistant,
+    hass_client: ClientSessionGenerator,
+    mock_connection: MockModbusConnection,
+    init_integration: MockConfigEntry,
+) -> None:
+    """Test a mask is assembled from four registers, most significant first."""
+    holding = mock_connection.for_unit(1).holding
+    holding[0x0400] = 0x0001
+    holding[0x0401] = 0x0002
+    holding[0x0402] = 0x0003
+    holding[0x0403] = 0x0004
+
+    diag = await get_diagnostics_for_config_entry(hass, hass_client, init_integration)
+
+    assert diag["address_masks"]["1024"] == 0x0001000200030004