diff --git a/dictionaries/CallMap.php b/dictionaries/CallMap.php
index 2c801dec9..4cd4dfc3d 100644
--- a/dictionaries/CallMap.php
+++ b/dictionaries/CallMap.php
@@ -11334,7 +11334,7 @@ return [
 'SimpleXMLElement::xpath' => ['SimpleXMLElement[]|false', 'path'=>'string'],
 'sin' => ['float', 'num'=>'float'],
 'sinh' => ['float', 'num'=>'float'],
-'sizeof' => ['int', 'value'=>'Countable|array', 'mode='=>'int'],
+'sizeof' => ['int<0, max>', 'value'=>'Countable|array', 'mode='=>'int'],
 'sleep' => ['int', 'seconds'=>'0|positive-int'],
 'snmp2_get' => ['string|false', 'hostname'=>'string', 'community'=>'string', 'object_id'=>'string', 'timeout='=>'int', 'retries='=>'int'],
 'snmp2_getnext' => ['string|false', 'hostname'=>'string', 'community'=>'string', 'object_id'=>'string', 'timeout='=>'int', 'retries='=>'int'],
diff --git a/dictionaries/CallMap_80_delta.php b/dictionaries/CallMap_80_delta.php
index b2cc5c427..9f3727636 100644
--- a/dictionaries/CallMap_80_delta.php
+++ b/dictionaries/CallMap_80_delta.php
@@ -497,6 +497,10 @@ return [
       'old' => ['int<0, max>', 'value'=>'Countable|array|SimpleXMLElement', 'mode='=>'int'],
       'new' => ['int<0, max>', 'value'=>'Countable|array', 'mode='=>'int'],
     ],
+    'sizeof' => [
+      'old' => ['int<0, max>', 'value'=>'Countable|array|SimpleXMLElement', 'mode='=>'int'],
+      'new' => ['int<0, max>', 'value'=>'Countable|array', 'mode='=>'int'],
+    ],
     'count_chars' => [
       'old' => ['array<int,int>|false', 'input'=>'string', 'mode='=>'0|1|2'],
       'new' => ['array<int,int>', 'input'=>'string', 'mode='=>'0|1|2'],
diff --git a/dictionaries/CallMap_historical.php b/dictionaries/CallMap_historical.php
index ca5028008..c58cb3d06 100644
--- a/dictionaries/CallMap_historical.php
+++ b/dictionaries/CallMap_historical.php
@@ -14030,7 +14030,7 @@ return [
     'simplexml_load_string' => ['SimpleXMLElement|false', 'data'=>'string', 'class_name='=>'?string', 'options='=>'int', 'namespace_or_prefix='=>'string', 'is_prefix='=>'bool'],
     'sin' => ['float', 'num'=>'float'],
     'sinh' => ['float', 'num'=>'float'],
-    'sizeof' => ['int', 'value'=>'Countable|array', 'mode='=>'int'],
+    'sizeof' => ['int<0, max>', 'value'=>'Countable|array|SimpleXMLElement', 'mode='=>'int'],
     'sleep' => ['int|false', 'seconds'=>'0|positive-int'],
     'snmp2_get' => ['string|false', 'hostname'=>'string', 'community'=>'string', 'object_id'=>'string', 'timeout='=>'int', 'retries='=>'int'],
     'snmp2_getnext' => ['string|false', 'hostname'=>'string', 'community'=>'string', 'object_id'=>'string', 'timeout='=>'int', 'retries='=>'int'],
diff --git a/src/Psalm/Internal/Analyzer/Statements/Expression/AssertionFinder.php b/src/Psalm/Internal/Analyzer/Statements/Expression/AssertionFinder.php
index cd3d910a9..5f4bcdf0f 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Expression/AssertionFinder.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Expression/AssertionFinder.php
@@ -1542,7 +1542,7 @@ class AssertionFinder
     ) {
         if ($conditional->left instanceof PhpParser\Node\Expr\FuncCall
             && $conditional->left->name instanceof PhpParser\Node\Name
-            && strtolower($conditional->left->name->parts[0]) === 'count'
+            && in_array(strtolower($conditional->left->name->parts[0]), ['count', 'sizeof'])
             && $conditional->left->getArgs()
             && ($conditional instanceof BinaryOp\Greater || $conditional instanceof BinaryOp\GreaterOrEqual)
         ) {
@@ -1551,7 +1551,7 @@ class AssertionFinder
             $comparison_adjustment = $conditional instanceof BinaryOp\Greater ? 1 : 0;
         } elseif ($conditional->right instanceof PhpParser\Node\Expr\FuncCall
             && $conditional->right->name instanceof PhpParser\Node\Name
-            && strtolower($conditional->right->name->parts[0]) === 'count'
+            && in_array(strtolower($conditional->right->name->parts[0]), ['count', 'sizeof'])
             && $conditional->right->getArgs()
             && ($conditional instanceof BinaryOp\Smaller || $conditional instanceof BinaryOp\SmallerOrEqual)
         ) {
@@ -1584,7 +1584,7 @@ class AssertionFinder
     ) {
         $left_count = $conditional->left instanceof PhpParser\Node\Expr\FuncCall
             && $conditional->left->name instanceof PhpParser\Node\Name
-            && strtolower($conditional->left->name->parts[0]) === 'count'
+            && in_array(strtolower($conditional->left->name->parts[0]), ['count', 'sizeof'])
             && $conditional->left->getArgs();
 
         $operator_less_than_or_equal =
@@ -1603,7 +1603,7 @@ class AssertionFinder
 
         $right_count = $conditional->right instanceof PhpParser\Node\Expr\FuncCall
             && $conditional->right->name instanceof PhpParser\Node\Name
-            && strtolower($conditional->right->name->parts[0]) === 'count'
+            && in_array(strtolower($conditional->right->name->parts[0]), ['count', 'sizeof'])
             && $conditional->right->getArgs();
 
         $operator_greater_than_or_equal =
@@ -1633,7 +1633,7 @@ class AssertionFinder
     ) {
         $left_count = $conditional->left instanceof PhpParser\Node\Expr\FuncCall
             && $conditional->left->name instanceof PhpParser\Node\Name
-            && strtolower($conditional->left->name->parts[0]) === 'count'
+            && in_array(strtolower($conditional->left->name->parts[0]), ['count', 'sizeof'])
             && $conditional->left->getArgs();
 
         if ($left_count && $conditional->right instanceof PhpParser\Node\Scalar\LNumber) {
@@ -1644,7 +1644,7 @@ class AssertionFinder
 
         $right_count = $conditional->right instanceof PhpParser\Node\Expr\FuncCall
             && $conditional->right->name instanceof PhpParser\Node\Name
-            && strtolower($conditional->right->name->parts[0]) === 'count'
+            && in_array(strtolower($conditional->right->name->parts[0]), ['count', 'sizeof'])
             && $conditional->right->getArgs();
 
         if ($right_count && $conditional->left instanceof PhpParser\Node\Scalar\LNumber) {
@@ -1785,7 +1785,7 @@ class AssertionFinder
     ) {
         $left_count = $conditional->left instanceof PhpParser\Node\Expr\FuncCall
             && $conditional->left->name instanceof PhpParser\Node\Name
-            && strtolower($conditional->left->name->parts[0]) === 'count';
+            && in_array(strtolower($conditional->left->name->parts[0]), ['count', 'sizeof']);
 
         $right_number = $conditional->right instanceof PhpParser\Node\Scalar\LNumber
             && $conditional->right->value === (
@@ -2044,7 +2044,8 @@ class AssertionFinder
 
     protected static function hasNonEmptyCountCheck(PhpParser\Node\Expr\FuncCall $stmt): bool
     {
-        return $stmt->name instanceof PhpParser\Node\Name && strtolower($stmt->name->parts[0]) === 'count';
+        return $stmt->name instanceof PhpParser\Node\Name &&
+            in_array(strtolower($stmt->name->parts[0]), ['count', 'sizeof']);
     }
 
     protected static function hasArrayKeyExistsCheck(PhpParser\Node\Expr\FuncCall $stmt): bool
diff --git a/src/Psalm/Internal/Analyzer/Statements/Expression/Call/FunctionCallReturnTypeFetcher.php b/src/Psalm/Internal/Analyzer/Statements/Expression/Call/FunctionCallReturnTypeFetcher.php
index 6c40bf783..76ba4f08c 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Expression/Call/FunctionCallReturnTypeFetcher.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Expression/Call/FunctionCallReturnTypeFetcher.php
@@ -354,6 +354,7 @@ class FunctionCallReturnTypeFetcher
         } else {
             switch ($call_map_key) {
                 case 'count':
+                case 'sizeof':
                     if (($first_arg_type = $statements_analyzer->node_data->getType($call_args[0]->value))) {
                         $atomic_types = $first_arg_type->getAtomicTypes();
 
diff --git a/src/Psalm/Internal/Analyzer/Statements/Expression/MatchAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/Expression/MatchAnalyzer.php
index 677d36a57..c16948048 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Expression/MatchAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Expression/MatchAnalyzer.php
@@ -81,7 +81,8 @@ class MatchAnalyzer
                 && ($stmt->cond->name->parts === ['get_class']
                     || $stmt->cond->name->parts === ['gettype']
                     || $stmt->cond->name->parts === ['get_debug_type']
-                    || $stmt->cond->name->parts === ['count'])
+                    || $stmt->cond->name->parts === ['count']
+                    || $stmt->cond->name->parts === ['sizeof'])
                 && $stmt->cond->getArgs()
             ) {
                 $first_arg = $stmt->cond->getArgs()[0];
diff --git a/src/Psalm/Internal/Codebase/Functions.php b/src/Psalm/Internal/Codebase/Functions.php
index 9ba277fec..50e3f60fb 100644
--- a/src/Psalm/Internal/Codebase/Functions.php
+++ b/src/Psalm/Internal/Codebase/Functions.php
@@ -555,7 +555,7 @@ class Functions
             return true;
         }
 
-        if ($function_id === 'count' && isset($args[0]) && $type_provider) {
+        if (in_array($function_id, ['count', 'sizeof']) && isset($args[0]) && $type_provider) {
             $count_type = $type_provider->getType($args[0]->value);
 
             if ($count_type) {
diff --git a/tests/ArrayAccessTest.php b/tests/ArrayAccessTest.php
index 113458d2d..1a9a63f1b 100644
--- a/tests/ArrayAccessTest.php
+++ b/tests/ArrayAccessTest.php
@@ -145,6 +145,22 @@ class ArrayAccessTest extends TestCase
         $this->analyzeFile('somefile.php', new Context());
     }
 
+    public function testNoIssueWhenUsingArrayValuesOnNonEmptyArrayCheckedWithSizeof(): void
+    {
+        Config::getInstance()->ensure_array_int_offsets_exist = true;
+
+        $this->addFile(
+            'somefile.php',
+            '<?php
+                /** @param string[][] $arr */
+                function foo(array $arr) : void {
+                    if (sizeof($arr) === 1 && sizeof(array_values($arr)[0]) === 1) {}
+                }',
+        );
+
+        $this->analyzeFile('somefile.php', new Context());
+    }
+
     public function testNoIssueAfterManyIssets(): void
     {
         Config::getInstance()->ensure_array_int_offsets_exist = true;