diff --git a/src/Reflection/Adapter/ReflectionProperty.php b/src/Reflection/Adapter/ReflectionProperty.php
index 526a4ce53..b4a6b10ef 100644
--- a/src/Reflection/Adapter/ReflectionProperty.php
+++ b/src/Reflection/Adapter/ReflectionProperty.php
@@ -165,6 +165,6 @@ public function getAttributes(?string $name = null, int $flags = 0): array
 
     public function isReadOnly(): bool
     {
-        throw new Exception\NotImplemented('Not implemented');
+        return $this->betterReflectionProperty->isReadOnly();
     }
 }
diff --git a/src/Reflection/ReflectionProperty.php b/src/Reflection/ReflectionProperty.php
index 5a136df3e..114d3ac97 100644
--- a/src/Reflection/ReflectionProperty.php
+++ b/src/Reflection/ReflectionProperty.php
@@ -230,6 +230,11 @@ public function isInitialized(?object $object = null): bool
         }
     }
 
+    public function isReadOnly(): bool
+    {
+        return $this->node->isReadonly();
+    }
+
     /**
      * Get the DocBlock type hints as an array of strings.
      *
diff --git a/src/Reflection/StringCast/ReflectionPropertyStringCast.php b/src/Reflection/StringCast/ReflectionPropertyStringCast.php
index 38c7565a3..125f42e87 100644
--- a/src/Reflection/StringCast/ReflectionPropertyStringCast.php
+++ b/src/Reflection/StringCast/ReflectionPropertyStringCast.php
@@ -24,10 +24,11 @@ public static function toString(ReflectionProperty $propertyReflection): string
         $type = $propertyReflection->getType();
 
         return sprintf(
-            'Property [%s %s%s%s $%s ]',
+            'Property [%s %s%s%s%s $%s ]',
             $stateModifier,
             self::visibilityToString($propertyReflection),
             $propertyReflection->isStatic() ? ' static' : '',
+            $propertyReflection->isReadOnly() ? ' readonly' : '',
             $type !== null ? sprintf(' %s', $type->__toString()) : '',
             $propertyReflection->getName(),
         );
diff --git a/test/unit/Fixture/ExampleClass.php b/test/unit/Fixture/ExampleClass.php
index 3396578aa..4bb969a2e 100644
--- a/test/unit/Fixture/ExampleClass.php
+++ b/test/unit/Fixture/ExampleClass.php
@@ -38,6 +38,8 @@ class ExampleClass
          */
         public $publicProperty = __DIR__;
 
+        public readonly int $readOnlyProperty;
+
         public static $publicStaticProperty;
 
         public function __construct(private ?int $promotedProperty = 123, $noPromotedProperty = null)
diff --git a/test/unit/Fixture/ExampleClassExport.txt b/test/unit/Fixture/ExampleClassExport.txt
index d3eb75dc7..7db04de83 100644
--- a/test/unit/Fixture/ExampleClassExport.txt
+++ b/test/unit/Fixture/ExampleClassExport.txt
@@ -1,5 +1,5 @@
 Class [ <user> class Roave\BetterReflectionTest\Fixture\ExampleClass ] {
-  @@ %s/test/unit/Fixture/ExampleClass.php 10-50
+  @@ %s/test/unit/Fixture/ExampleClass.php 10-52
 
   - Constants [5] {
     Constant [ public integer MY_CONST_1 ] { 123 }
@@ -16,16 +16,17 @@ Class [ <user> class Roave\BetterReflectionTest\Fixture\ExampleClass ] {
   - Static methods [0] {
   }
 
-  - Properties [4] {
+  - Properties [5] {
     Property [ <default> private $privateProperty ]
     Property [ <default> protected $protectedProperty ]
     Property [ <default> public $publicProperty ]
+    Property [ <default> public readonly int $readOnlyProperty ]
     Property [ <default> private ?int $promotedProperty ]
   }
 
   - Methods [2] {
     Method [ <user, ctor> public method __construct ] {
-      @@ %s/test/unit/Fixture/ExampleClass.php 43 - 45
+      @@ %s/test/unit/Fixture/ExampleClass.php 45 - 47
 
       - Parameters [2] {
         Parameter #0 [ <optional> ?int $promotedProperty = 123 ]
@@ -34,7 +35,7 @@ Class [ <user> class Roave\BetterReflectionTest\Fixture\ExampleClass ] {
     }
 
     Method [ <user> public method someMethod ] {
-      @@ %s/test/unit/Fixture/ExampleClass.php 47 - 49
+      @@ %s/test/unit/Fixture/ExampleClass.php 49 - 51
     }
   }
 }
diff --git a/test/unit/Fixture/StringCastClass.php b/test/unit/Fixture/StringCastClass.php
index 38a3fab69..32965af28 100644
--- a/test/unit/Fixture/StringCastClass.php
+++ b/test/unit/Fixture/StringCastClass.php
@@ -39,6 +39,8 @@ abstract class StringCastClass extends StringCastClassParent implements StringCa
     public int|bool $unionTypeProperty = false;
     public ?int $nullableTypeProperty = null;
 
+    public readonly int $readOnlyProperty;
+
     public function __construct()
     {
     }
diff --git a/test/unit/Fixture/StringCastClassExpected.txt b/test/unit/Fixture/StringCastClassExpected.txt
index 8202d1e9e..aaf1172fa 100644
--- a/test/unit/Fixture/StringCastClassExpected.txt
+++ b/test/unit/Fixture/StringCastClassExpected.txt
@@ -1,5 +1,5 @@
 Class [ <user> abstract class Roave\BetterReflectionTest\Fixture\StringCastClass extends Roave\BetterReflectionTest\Fixture\StringCastClassParent implements Roave\BetterReflectionTest\Fixture\StringCastClassInterface2, Roave\BetterReflectionTest\Fixture\StringCastClassInterface ] {
-  @@ %s/Fixture/StringCastClass.php 26-87
+  @@ %s/Fixture/StringCastClass.php 26-89
 
   - Constants [4] {
     Constant [ public boolean PUBLIC_CONSTANT ] { 1 }
@@ -14,62 +14,63 @@ Class [ <user> abstract class Roave\BetterReflectionTest\Fixture\StringCastClass
 
   - Static methods [1] {
     Method [ <user> static public method staticPublicMethod ] {
-      @@ %s/Fixture/StringCastClass.php 68 - 70
+      @@ %s/Fixture/StringCastClass.php 70 - 72
     }
   }
 
-  - Properties [6] {
+  - Properties [7] {
     Property [ <default> private $privateProperty ]
     Property [ <default> protected $protectedProperty ]
     Property [ <default> public $publicProperty ]
     Property [ <default> public int $namedTypeProperty ]
     Property [ <default> public int|bool $unionTypeProperty ]
     Property [ <default> public ?int $nullableTypeProperty ]
+    Property [ <default> public readonly int $readOnlyProperty ]
   }
 
   - Methods [12] {
     Method [ <user, ctor> public method __construct ] {
-      @@ %s/Fixture/StringCastClass.php 42 - 44
+      @@ %s/Fixture/StringCastClass.php 44 - 46
     }
 
     Method [ <user, dtor> public method __destruct ] {
-      @@ %s/Fixture/StringCastClass.php 46 - 48
+      @@ %s/Fixture/StringCastClass.php 48 - 50
     }
 
     Method [ <user> public method publicMethod ] {
-      @@ %s/Fixture/StringCastClass.php 50 - 52
+      @@ %s/Fixture/StringCastClass.php 52 - 54
     }
 
     Method [ <user> protected method protectedMethod ] {
-      @@ %s/Fixture/StringCastClass.php 54 - 56
+      @@ %s/Fixture/StringCastClass.php 56 - 58
     }
 
     Method [ <user> private method privateMethod ] {
-      @@ %s/Fixture/StringCastClass.php 58 - 60
+      @@ %s/Fixture/StringCastClass.php 60 - 62
     }
 
     Method [ <user> final public method finalPublicMethod ] {
-      @@ %s/Fixture/StringCastClass.php 62 - 64
+      @@ %s/Fixture/StringCastClass.php 64 - 66
     }
 
     Method [ <user> abstract public method abstractPublicMethod ] {
-      @@ %s/Fixture/StringCastClass.php 66 - 66
+      @@ %s/Fixture/StringCastClass.php 68 - 68
     }
 
     Method [ <user> public method noVisibility ] {
-      @@ %s/Fixture/StringCastClass.php 72 - 74
+      @@ %s/Fixture/StringCastClass.php 74 - 76
     }
 
     Method [ <user, overwrites Roave\BetterReflectionTest\Fixture\StringCastClassParent, prototype Roave\BetterReflectionTest\Fixture\StringCastClassParent> public method overwrittenMethod ] {
-      @@ %s/Fixture/StringCastClass.php 76 - 78
+      @@ %s/Fixture/StringCastClass.php 78 - 80
     }
 
     Method [ <user, prototype Roave\BetterReflectionTest\Fixture\StringCastClassInterface> public method prototypeMethod ] {
-      @@ %s/Fixture/StringCastClass.php 80 - 82
+      @@ %s/Fixture/StringCastClass.php 82 - 84
     }
 
     Method [ <user> public method methodWithParameters ] {
-      @@ %s/Fixture/StringCastClass.php 84 - 86
+      @@ %s/Fixture/StringCastClass.php 86 - 88
 
       - Parameters [2] {
         Parameter #0 [ <required> $a ]
diff --git a/test/unit/Fixture/StringCastProperties.php b/test/unit/Fixture/StringCastProperties.php
index 4647f9e91..cfc1fff34 100644
--- a/test/unit/Fixture/StringCastProperties.php
+++ b/test/unit/Fixture/StringCastProperties.php
@@ -12,4 +12,6 @@ class StringCastProperties
     public int $namedTypeProperty = 0;
     public int|bool $unionTypeProperty = false;
     public ?int $nullableTypeProperty = null;
+
+    public readonly int $readOnlyProperty;
 }
diff --git a/test/unit/Reflection/Adapter/ReflectionPropertyTest.php b/test/unit/Reflection/Adapter/ReflectionPropertyTest.php
index b47ceb406..948c9a8de 100644
--- a/test/unit/Reflection/Adapter/ReflectionPropertyTest.php
+++ b/test/unit/Reflection/Adapter/ReflectionPropertyTest.php
@@ -66,7 +66,7 @@ public function methodExpectationProvider(): array
             ['getDefaultValue', null, null, []],
             ['isPromoted', null, true, []],
             ['getAttributes', NotImplemented::class, null, []],
-            ['isReadOnly', NotImplemented::class, null, []],
+            ['isReadOnly', null, true, []],
         ];
     }
 
diff --git a/test/unit/Reflection/ReflectionClassTest.php b/test/unit/Reflection/ReflectionClassTest.php
index cb56a8987..c67c17a5f 100644
--- a/test/unit/Reflection/ReflectionClassTest.php
+++ b/test/unit/Reflection/ReflectionClassTest.php
@@ -386,7 +386,7 @@ public function testGetProperties(): void
         $properties = $classInfo->getProperties();
 
         self::assertContainsOnlyInstancesOf(ReflectionProperty::class, $properties);
-        self::assertCount(5, $properties);
+        self::assertCount(6, $properties);
     }
 
     public function testGetPropertiesDeclaredWithOneKeyword(): void
@@ -418,7 +418,7 @@ public function getPropertiesWithFilterDataProvider(): array
     {
         return [
             [CoreReflectionProperty::IS_STATIC, 1],
-            [CoreReflectionProperty::IS_PUBLIC, 2],
+            [CoreReflectionProperty::IS_PUBLIC, 3],
             [CoreReflectionProperty::IS_PROTECTED, 1],
             [CoreReflectionProperty::IS_PRIVATE, 2],
             [
@@ -426,7 +426,7 @@ public function getPropertiesWithFilterDataProvider(): array
                 CoreReflectionProperty::IS_PUBLIC |
                 CoreReflectionProperty::IS_PROTECTED |
                 CoreReflectionProperty::IS_PRIVATE,
-                5,
+                6,
             ],
         ];
     }
diff --git a/test/unit/Reflection/ReflectionPropertyTest.php b/test/unit/Reflection/ReflectionPropertyTest.php
index 9ea5df9c0..31e484942 100644
--- a/test/unit/Reflection/ReflectionPropertyTest.php
+++ b/test/unit/Reflection/ReflectionPropertyTest.php
@@ -100,6 +100,17 @@ public function testIsStatic(): void
         self::assertTrue($staticProp->isStatic());
     }
 
+    public function testIsReadOnly(): void
+    {
+        $classInfo = $this->reflector->reflectClass(ExampleClass::class);
+
+        $notReadOnlyProperty = $classInfo->getProperty('publicProperty');
+        self::assertFalse($notReadOnlyProperty->isReadOnly());
+
+        $readOnlyProperty = $classInfo->getProperty('readOnlyProperty');
+        self::assertTrue($readOnlyProperty->isReadOnly());
+    }
+
     /**
      * @return array
      */
diff --git a/test/unit/Reflection/StringCast/ReflectionPropertyStringCastTest.php b/test/unit/Reflection/StringCast/ReflectionPropertyStringCastTest.php
index bc897bb79..356bc86fc 100644
--- a/test/unit/Reflection/StringCast/ReflectionPropertyStringCastTest.php
+++ b/test/unit/Reflection/StringCast/ReflectionPropertyStringCastTest.php
@@ -35,6 +35,7 @@ public function toStringProvider(): array
             ['namedTypeProperty', 'Property [ <default> public int $namedTypeProperty ]'],
             ['unionTypeProperty', 'Property [ <default> public int|bool $unionTypeProperty ]'],
             ['nullableTypeProperty', 'Property [ <default> public ?int $nullableTypeProperty ]'],
+            ['readOnlyProperty', 'Property [ <default> public readonly int $readOnlyProperty ]'],
         ];
     }