diff --git a/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/multibyte_offset_strpos.php.inc b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/multibyte_offset_strpos.php.inc
new file mode 100644
index 00000000000..512f49c6be3
--- /dev/null
+++ b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/multibyte_offset_strpos.php.inc
@@ -0,0 +1,25 @@
+<?php
+
+namespace Rector\Tests\Php80\Rector\NotIdentical\StrContainsRector\Fixture;
+
+class MultibyteOffsetStrpos
+{
+    public function run()
+    {
+        $isMatch = mb_strpos('happy 😊 euro €', 'e', 8) !== false;
+    }
+}
+?>
+-----
+<?php
+
+namespace Rector\Tests\Php80\Rector\NotIdentical\StrContainsRector\Fixture;
+
+class MultibyteOffsetStrpos
+{
+    public function run()
+    {
+        $isMatch = str_contains(mb_substr('happy 😊 euro €', 8), 'e');
+    }
+}
+?>
diff --git a/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/multibyte_strpos_function.php.inc b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/multibyte_strpos_function.php.inc
new file mode 100644
index 00000000000..6be2ada369e
--- /dev/null
+++ b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/multibyte_strpos_function.php.inc
@@ -0,0 +1,27 @@
+<?php
+
+namespace Rector\Tests\Php80\Rector\NotIdentical\StrContainsRector\Fixture;
+
+class MultibyteStrposFunction
+{
+    public function run()
+    {
+        $isMatch = mb_strpos('happy 😊 euro €', 'a') !== false;
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\Php80\Rector\NotIdentical\StrContainsRector\Fixture;
+
+class MultibyteStrposFunction
+{
+    public function run()
+    {
+        $isMatch = str_contains('happy 😊 euro €', 'a');
+    }
+}
+
+?>
diff --git a/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/multibyte_strstr_function.php.inc b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/multibyte_strstr_function.php.inc
new file mode 100644
index 00000000000..4fbe0e69e62
--- /dev/null
+++ b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/multibyte_strstr_function.php.inc
@@ -0,0 +1,27 @@
+<?php
+
+namespace Rector\Tests\Php80\Rector\NotIdentical\StrContainsRector\Fixture;
+
+class MultibyteStrstrFunction
+{
+    public function run()
+    {
+        $isMatch = mb_strstr('happy 😊 euro €', 'a') === false;
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\Php80\Rector\NotIdentical\StrContainsRector\Fixture;
+
+class MultibyteStrstrFunction
+{
+    public function run()
+    {
+        $isMatch = !str_contains('happy 😊 euro €', 'a');
+    }
+}
+
+?>
diff --git a/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/offset_variable_equal_multibyte_strpos.php.inc b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/offset_variable_equal_multibyte_strpos.php.inc
new file mode 100644
index 00000000000..deefc9315c9
--- /dev/null
+++ b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/offset_variable_equal_multibyte_strpos.php.inc
@@ -0,0 +1,27 @@
+<?php
+
+namespace Rector\Tests\Php80\Rector\NotIdentical\StrContainsRector\Fixture;
+
+class OffsetVariableMultibyteStrpos
+{
+    public function run()
+    {
+        $offset = 1;
+        $isMatch = mb_strpos('happy 😊 euro €', 'a', $offset) != false;
+    }
+}
+?>
+-----
+<?php
+
+namespace Rector\Tests\Php80\Rector\NotIdentical\StrContainsRector\Fixture;
+
+class OffsetVariableMultibyteStrpos
+{
+    public function run()
+    {
+        $offset = 1;
+        $isMatch = str_contains(mb_substr('happy 😊 euro €', $offset), 'a');
+    }
+}
+?>
diff --git a/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/replace_multibyte_strpos_with_encoding_null.php.inc b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/replace_multibyte_strpos_with_encoding_null.php.inc
new file mode 100644
index 00000000000..f1093ee5308
--- /dev/null
+++ b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/replace_multibyte_strpos_with_encoding_null.php.inc
@@ -0,0 +1,27 @@
+<?php
+
+namespace Rector\Tests\Php80\Rector\NotIdentical\StrContainsRector\Fixture;
+
+class ReplaceMultibyteStrposWithEncodingNull
+{
+    public function run()
+    {
+        $isMatch = mb_strpos('happy 😊 euro €', 'a', 0, null) !== false;
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\Php80\Rector\NotIdentical\StrContainsRector\Fixture;
+
+class ReplaceMultibyteStrposWithEncodingNull
+{
+    public function run()
+    {
+        $isMatch = str_contains('happy 😊 euro €', 'a');
+    }
+}
+
+?>
diff --git a/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/replace_multibyte_strstr_with_encoding_null.php.inc b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/replace_multibyte_strstr_with_encoding_null.php.inc
new file mode 100644
index 00000000000..0f689947e13
--- /dev/null
+++ b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/replace_multibyte_strstr_with_encoding_null.php.inc
@@ -0,0 +1,27 @@
+<?php
+
+namespace Rector\Tests\Php80\Rector\NotIdentical\StrContainsRector\Fixture;
+
+class ReplaceMultibyteStrstrWithEncodingNull
+{
+    public function run()
+    {
+        $isMatch = mb_strstr('happy 😊 euro €', 'a', false, null) !== false;
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\Php80\Rector\NotIdentical\StrContainsRector\Fixture;
+
+class ReplaceMultibyteStrstrWithEncodingNull
+{
+    public function run()
+    {
+        $isMatch = str_contains('happy 😊 euro €', 'a');
+    }
+}
+
+?>
diff --git a/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/skip_multibyte_strpos_with_encoding.php.inc b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/skip_multibyte_strpos_with_encoding.php.inc
new file mode 100644
index 00000000000..bc687adc4e7
--- /dev/null
+++ b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/skip_multibyte_strpos_with_encoding.php.inc
@@ -0,0 +1,13 @@
+<?php
+
+namespace Rector\Tests\Php80\Rector\NotIdentical\StrContainsRector\Fixture;
+
+class SkipMultibyteStrposWithEncoding
+{
+    public function run()
+    {
+        $isMatch = mb_strpos('happy 😊 euro €', 'a', 0, 'UTF-8') !== false;
+    }
+}
+
+?>
diff --git a/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/skip_multibyte_strstr_with_dynamic_encoding.php.inc b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/skip_multibyte_strstr_with_dynamic_encoding.php.inc
new file mode 100644
index 00000000000..5fe97330597
--- /dev/null
+++ b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/skip_multibyte_strstr_with_dynamic_encoding.php.inc
@@ -0,0 +1,13 @@
+<?php
+
+namespace Rector\Tests\Php80\Rector\NotIdentical\StrContainsRector\Fixture;
+
+class SkipMultibyteStrstrWithDynamicEncoding
+{
+    public function run(?string $encoding = 'UTF-8')
+    {
+        $isMatch = mb_strstr('happy 😊 euro €', 'a', false, $encoding) !== false;
+    }
+}
+
+?>
diff --git a/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/skip_multibyte_strstr_with_encoding.php.inc b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/skip_multibyte_strstr_with_encoding.php.inc
new file mode 100644
index 00000000000..0060403bcbf
--- /dev/null
+++ b/rules-tests/Php80/Rector/NotIdentical/StrContainsRector/Fixture/skip_multibyte_strstr_with_encoding.php.inc
@@ -0,0 +1,13 @@
+<?php
+
+namespace Rector\Tests\Php80\Rector\NotIdentical\StrContainsRector\Fixture;
+
+class SkipMultibyteStrstrWithEncoding
+{
+    public function run()
+    {
+        $isMatch = mb_strstr('happy 😊 euro €', 'a', false, 'UTF-8') !== false;
+    }
+}
+
+?>
diff --git a/rules/Php80/Rector/NotIdentical/StrContainsRector.php b/rules/Php80/Rector/NotIdentical/StrContainsRector.php
index 035e2ec6d8e..7daa7d7c11d 100644
--- a/rules/Php80/Rector/NotIdentical/StrContainsRector.php
+++ b/rules/Php80/Rector/NotIdentical/StrContainsRector.php
@@ -32,7 +32,7 @@ final class StrContainsRector extends AbstractRector implements MinPhpVersionInt
     /**
      * @var string[]
      */
-    private const OLD_STR_NAMES = ['strpos', 'strstr'];
+    private const OLD_STR_NAMES = ['mb_strpos', 'mb_strstr', 'strpos', 'strstr'];
 
     public function __construct(
         private readonly ValueResolver $valueResolver
@@ -47,7 +47,7 @@ public function provideMinPhpVersion(): int
     public function getRuleDefinition(): RuleDefinition
     {
         return new RuleDefinition(
-            'Replace strpos() !== false and strstr()  with str_contains()',
+            'Replace strpos|mb_strpos() !== false and strstr()|mb_strstr() with str_contains()',
             [
                 new CodeSample(
                     <<<'CODE_SAMPLE'
@@ -97,12 +97,20 @@ public function refactor(Node $node): ?Node
             return null;
         }
 
+        if ($this->isNames($funcCall->name, ['mb_strpos', 'mb_strstr']) && isset($funcCall->getArgs()[3])) {
+            if (! $this->valueResolver->isNull($funcCall->getArgs()[3]->value)) {
+                return null;
+            }
+
+            unset($funcCall->args[3]);
+        }
+
         if (isset($funcCall->getArgs()[2])) {
             $secondArg = $funcCall->getArgs()[2];
 
-            if ($this->isName($funcCall->name, 'strpos') && ! $this->isIntegerZero($secondArg->value)) {
+            if ($this->isNames($funcCall->name, ['strpos', 'mb_strpos']) && ! $this->isIntegerZero($secondArg->value)) {
                 $funcCall->args[0] = new Arg($this->nodeFactory->createFuncCall(
-                    'substr',
+                    $this->isName($funcCall->name, 'strpos') ? 'substr' : 'mb_substr',
                     [$funcCall->args[0], $secondArg]
                 ));
             }