diff --git a/src/Mailgun/Connection/RestClient.php b/src/Mailgun/Connection/RestClient.php
index 849b981..0a67bbb 100644
--- a/src/Mailgun/Connection/RestClient.php
+++ b/src/Mailgun/Connection/RestClient.php
@@ -261,15 +261,27 @@ class RestClient
     protected function prepareFile($fieldName, $filePath, $fileIndex=0)
     {
         $filename = null;
-        // Backward compatibility code
-        if (is_array($filePath)) {
-            $filename = $filePath['remoteName'];
-            $filePath = $filePath['filePath'];
-        }
+        $resource = null;
 
-        // Remove leading @ symbol
-        if (strpos($filePath, '@') === 0) {
-            $filePath = substr($filePath, 1);
+        if (is_array($filePath) && isset($filePath['fileContent'])) {
+            // File from memory
+            $filename = $filePath['filename'];
+            $resource = fopen('php://temp', 'r+');
+            fwrite($resource, $filePath['fileContent']);
+            rewind($resource);
+        } else {
+            // Backward compatibility code
+            if (is_array($filePath) && isset($filePath['filePath'])) {
+                $filename = $filePath['remoteName'];
+                $filePath = $filePath['filePath'];
+            }
+
+            // Remove leading @ symbol
+            if (strpos($filePath, '@') === 0) {
+                $filePath = substr($filePath, 1);
+            }
+
+            $resource = fopen($filePath, 'r');
         }
 
         // Add index for multiple file support
@@ -277,7 +289,7 @@ class RestClient
 
         return [
             'name'     => $fieldName,
-            'contents' => fopen($filePath, 'r'),
+            'contents' => $resource,
             'filename' => $filename,
         ];
     }
diff --git a/tests/Functional/FileFromMemoryTest.php b/tests/Functional/FileFromMemoryTest.php
new file mode 100644
index 0000000..484f2e6
--- /dev/null
+++ b/tests/Functional/FileFromMemoryTest.php
@@ -0,0 +1,50 @@
+<?php
+
+namespace Mailgun\Tests\Functional;
+
+/**
+ * Add attachment with file from memory
+ *
+ * @author Wim Verstuyf <wim.verstuyf@codelicious.be>
+ */
+class FileFromMemoryTest extends \PHPUnit_Framework_TestCase
+{
+    public function testAddFileFromMemory()
+    {
+        $fileValidator = function($files) {
+            // Get only the attachments so the properties can be converted to a format we like
+            $attachments = array_filter($files, function($f) {
+                return strpos($f['name'], 'attachment') !== false;
+            });
+
+            // Convert resources to strings
+            $attachments = array_map(function($f) {
+                return [
+                    'name' => $f['name'],
+                    'contents' => fread($f['contents'], 50),
+                    'filename' => $f['filename'],
+                ];
+            }, $attachments);
+
+            $this->assertContains(['name'=>'attachment[0]', 'contents'=>'File content', 'filename' => 'file1.txt'], $attachments);
+            $this->assertContains(['name'=>'attachment[1]', 'contents'=>'File content 2', 'filename' => 'file2.txt'], $attachments);
+            $this->assertContains(['name'=>'attachment[2]', 'contents'=>'Contents of a text file', 'filename' => 'text_file.txt'], $attachments); 
+        };
+
+        $attachments = [
+            ['filename' => 'file1.txt', 'fileContent' => "File content"],
+            ['filename' => 'file2.txt', 'fileContent' => "File content 2"],
+            ['filePath' => "./tests/TestAssets/text_file.txt", 'remoteName' => 'text_file.txt']
+        ];
+
+        $mailgun = MockedMailgun::create($this, 'POST', 'domain/messages', [], $fileValidator);
+
+        $mailgun->sendMessage('domain', array(
+            'from'    => 'bob@example.com',
+            'to'      => 'alice@example.com',
+            'subject' => 'Foo',
+            'text'    => 'Bar'), array(
+            'attachment' => $attachments
+            ));
+    }
+}
diff --git a/tests/TestAssets/text_file.txt b/tests/TestAssets/text_file.txt
new file mode 100644
index 0000000..b1108c6
--- /dev/null
+++ b/tests/TestAssets/text_file.txt
@@ -0,0 +1 @@
+Contents of a text file
\ No newline at end of file