diff --git a/src/Psalm/Internal/Provider/ReturnTypeProvider/StrReplaceReturnTypeProvider.php b/src/Psalm/Internal/Provider/ReturnTypeProvider/StrReplaceReturnTypeProvider.php
index 2dfa3681691..6b5270e40d5 100644
--- a/src/Psalm/Internal/Provider/ReturnTypeProvider/StrReplaceReturnTypeProvider.php
+++ b/src/Psalm/Internal/Provider/ReturnTypeProvider/StrReplaceReturnTypeProvider.php
@@ -10,6 +10,7 @@
 use Psalm\Type\Atomic\TString;
 use Psalm\Type\Union;
 
+use function call_user_func;
 use function count;
 use function in_array;
 
@@ -50,7 +51,24 @@ public static function getFunctionReturnType(FunctionReturnTypeProviderEvent $ev
 
             $return_type = Type::getString();
 
-            if (in_array($function_id, ['preg_replace', 'preg_replace_callback'], true)) {
+            if (in_array($function_id, ['str_replace', 'str_ireplace'], true)
+                && $subject_type->isSingleStringLiteral()
+            ) {
+                $first_arg = $statements_source->node_data->getType($call_args[0]->value);
+                $second_arg = $statements_source->node_data->getType($call_args[1]->value);
+                if ($first_arg && $second_arg && $first_arg->isSingleStringLiteral() && $second_arg->isSingleStringLiteral()) {
+                    /**
+                     * @var string $replaced_string
+                     */
+                    $replaced_string = call_user_func(
+                        $function_id,
+                        $first_arg->getSingleStringLiteral()->value,
+                        $second_arg->getSingleStringLiteral()->value,
+                        $subject_type->getSingleStringLiteral()->value
+                    );
+                    $return_type = Type::getString($replaced_string);
+                }
+            } elseif (in_array($function_id, ['preg_replace', 'preg_replace_callback'], true)) {
                 $return_type = new Union([new TString, new TNull()]);
 
                 $codebase = $statements_source->getCodebase();