diff --git a/bundles/org.openhab.binding.matter/src/main/java/org/openhab/binding/matter/internal/controller/devices/converter/IlluminanceMeasurementConverter.java b/bundles/org.openhab.binding.matter/src/main/java/org/openhab/binding/matter/internal/controller/devices/converter/IlluminanceMeasurementConverter.java
index ec7319b0f3..a9c8ae3fca 100644
--- a/bundles/org.openhab.binding.matter/src/main/java/org/openhab/binding/matter/internal/controller/devices/converter/IlluminanceMeasurementConverter.java
+++ b/bundles/org.openhab.binding.matter/src/main/java/org/openhab/binding/matter/internal/controller/devices/converter/IlluminanceMeasurementConverter.java
@@ -17,15 +17,13 @@ import static org.openhab.binding.matter.internal.MatterBindingConstants.*;
 import java.util.Collections;
 import java.util.Map;
 
-import javax.measure.quantity.Illuminance;
-
 import org.eclipse.jdt.annotation.NonNullByDefault;
 import org.eclipse.jdt.annotation.Nullable;
 import org.openhab.binding.matter.internal.client.dto.cluster.gen.IlluminanceMeasurementCluster;
 import org.openhab.binding.matter.internal.client.dto.ws.AttributeChangedMessage;
 import org.openhab.binding.matter.internal.handler.MatterBaseThingHandler;
+import org.openhab.binding.matter.internal.util.ValueUtils;
 import org.openhab.core.library.types.QuantityType;
-import org.openhab.core.library.unit.Units;
 import org.openhab.core.thing.Channel;
 import org.openhab.core.thing.ChannelGroupUID;
 import org.openhab.core.thing.ChannelUID;
@@ -61,8 +59,8 @@ public class IlluminanceMeasurementConverter extends GenericConverter<Illuminanc
         switch (message.path.attributeName) {
             case IlluminanceMeasurementCluster.ATTRIBUTE_MEASURED_VALUE:
                 if (message.value instanceof Number number) {
-                    updateState(CHANNEL_ID_ILLUMINANCEMEASURMENT_MEASUREDVALUE,
-                            new QuantityType<Illuminance>(number.intValue(), Units.LUX));
+                    QuantityType<?> lux = ValueUtils.valueToIlluminance(number.intValue());
+                    updateState(CHANNEL_ID_ILLUMINANCEMEASURMENT_MEASUREDVALUE, lux != null ? lux : UnDefType.NULL);
                 }
                 break;
         }
@@ -71,9 +69,9 @@ public class IlluminanceMeasurementConverter extends GenericConverter<Illuminanc
 
     @Override
     public void initState() {
-        updateState(CHANNEL_ID_ILLUMINANCEMEASURMENT_MEASUREDVALUE,
-                initializingCluster.measuredValue != null
-                        ? new QuantityType<Illuminance>(initializingCluster.measuredValue, Units.LUX)
-                        : UnDefType.NULL);
+        QuantityType<?> lux = initializingCluster.measuredValue != null
+                ? ValueUtils.valueToIlluminance(initializingCluster.measuredValue)
+                : null;
+        updateState(CHANNEL_ID_ILLUMINANCEMEASURMENT_MEASUREDVALUE, lux != null ? lux : UnDefType.NULL);
     }
 }
diff --git a/bundles/org.openhab.binding.matter/src/main/java/org/openhab/binding/matter/internal/util/ValueUtils.java b/bundles/org.openhab.binding.matter/src/main/java/org/openhab/binding/matter/internal/util/ValueUtils.java
index 0568863947..b7444c6a16 100644
--- a/bundles/org.openhab.binding.matter/src/main/java/org/openhab/binding/matter/internal/util/ValueUtils.java
+++ b/bundles/org.openhab.binding.matter/src/main/java/org/openhab/binding/matter/internal/util/ValueUtils.java
@@ -15,6 +15,7 @@ package org.openhab.binding.matter.internal.util;
 import java.math.BigDecimal;
 import java.math.RoundingMode;
 
+import javax.measure.quantity.Illuminance;
 import javax.measure.quantity.Temperature;
 
 import org.eclipse.jdt.annotation.NonNullByDefault;
@@ -23,6 +24,7 @@ import org.openhab.core.library.types.PercentType;
 import org.openhab.core.library.types.QuantityType;
 import org.openhab.core.library.unit.ImperialUnits;
 import org.openhab.core.library.unit.SIUnits;
+import org.openhab.core.library.unit.Units;
 import org.openhab.core.types.Type;
 
 /**
@@ -94,4 +96,23 @@ public class ValueUtils {
     public static QuantityType<Temperature> valueToTemperature(int value) {
         return new QuantityType<>(BigDecimal.valueOf(value, 2), SIUnits.CELSIUS);
     }
+
+    /**
+     * Converts a Matter illuminance measurement value to a {@link QuantityType} in lux.
+     * The Matter spec encodes illuminance as: MeasuredValue = 10,000 x log10(illuminance) + 1
+     * A value of 0 indicates illuminance too low to be measured.
+     *
+     * @param value the Matter measured value (0 = too low, 1-0xFFFE = encoded illuminance)
+     * @return the {@link QuantityType} in lux
+     */
+    public static @Nullable QuantityType<Illuminance> valueToIlluminance(int value) {
+        if (value <= 0) {
+            return new QuantityType<>(0, Units.LUX);
+        }
+        if (value > 0xFFFE) {
+            return null;
+        }
+        double illuminance = Math.pow(10, (value - 1) / 10000.0);
+        return new QuantityType<>(illuminance, Units.LUX);
+    }
 }
diff --git a/bundles/org.openhab.binding.matter/src/test/java/org/openhab/binding/matter/internal/controller/devices/converter/IlluminanceMeasurementConverterTest.java b/bundles/org.openhab.binding.matter/src/test/java/org/openhab/binding/matter/internal/controller/devices/converter/IlluminanceMeasurementConverterTest.java
index 9a19d3b973..d7b068e830 100644
--- a/bundles/org.openhab.binding.matter/src/test/java/org/openhab/binding/matter/internal/controller/devices/converter/IlluminanceMeasurementConverterTest.java
+++ b/bundles/org.openhab.binding.matter/src/test/java/org/openhab/binding/matter/internal/controller/devices/converter/IlluminanceMeasurementConverterTest.java
@@ -72,18 +72,20 @@ class IlluminanceMeasurementConverterTest extends BaseMatterConverterTest {
         AttributeChangedMessage message = new AttributeChangedMessage();
         message.path = new Path();
         message.path.attributeName = "measuredValue";
-        message.value = 100;
+        message.value = 10001;
         converter.onEvent(message);
+        // 10001 -> 10^((10001-1)/10000) = 10^1 = 10 lux
         verify(mockHandler, times(1)).updateState(eq(1), eq("illuminancemeasurement-measuredvalue"),
-                eq(new QuantityType<Illuminance>(100, Units.LUX)));
+                eq(new QuantityType<Illuminance>(10.0, Units.LUX)));
     }
 
     @Test
     void testInitState() {
-        mockCluster.measuredValue = 100;
+        mockCluster.measuredValue = 20001;
         converter.initState();
+        // 20001 -> 10^((20001-1)/10000) = 10^2 = 100 lux
         verify(mockHandler, times(1)).updateState(eq(1), eq("illuminancemeasurement-measuredvalue"),
-                eq(new QuantityType<Illuminance>(100, Units.LUX)));
+                eq(new QuantityType<Illuminance>(100.0, Units.LUX)));
     }
 
     @Test