diff --git a/config/services.yaml b/config/services.yaml
index 9e158ff6..2ce270f7 100644
--- a/config/services.yaml
+++ b/config/services.yaml
@@ -42,6 +42,11 @@ services:
         tags:
             - { name: doctrine.orm.entity_listener }
 
+    attachment_delete_listener:
+        class: App\EntityListeners\AttachmentDeleteListener
+        tags:
+            - name: doctrine.orm.entity_listener
+
 
     App\Command\UpdateExchangeRatesCommand:
         arguments:
diff --git a/src/Entity/Attachments/Attachment.php b/src/Entity/Attachments/Attachment.php
index d3508c35..00daf724 100644
--- a/src/Entity/Attachments/Attachment.php
+++ b/src/Entity/Attachments/Attachment.php
@@ -37,6 +37,7 @@ use Symfony\Component\Validator\Constraints as Assert;
  * @ORM\InheritanceType("SINGLE_TABLE")
  * @ORM\DiscriminatorColumn(name="class_name", type="string")
  * @ORM\DiscriminatorMap({"PartDB\Part" = "PartAttachment", "Part" = "PartAttachment"})
+ * @ORM\EntityListeners({"App\EntityListeners\AttachmentDeleteListener"})
  *
  */
 abstract class Attachment extends NamedDBElement
@@ -124,17 +125,6 @@ abstract class Attachment extends NamedDBElement
         return $this->element;
     }
 
-    /**
-     * Checks if the file in this attachement is existing. This works for files on the HDD, and for URLs
-     * (it's not checked if the ressource behind the URL is really existing).
-     *
-     * @return bool True if the file is existing.
-     */
-    public function isFileExisting(): bool
-    {
-        return file_exists($this->getPath()) || static::isURL($this->getPath());
-    }
-
     /**
      * The URL to the external file.
      * Returns null, if the file is not external.
@@ -273,11 +263,11 @@ abstract class Attachment extends NamedDBElement
     {
         //Only set if the URL is not empty
         if (!empty($url)) {
-            $this->path = $url;
-        }
+            if (strpos($url, '%BASE%') !== false || strpos($url, '%MEDIA%') !== false) {
+                throw new \InvalidArgumentException("You can not reference internal files via the url field! But nice try!");
+            }
 
-        if (strpos($url, '%BASE%') !== false || strpos($url, '%MEDIA%') !== false) {
-            throw new \InvalidArgumentException("You can not reference internal files via the url field! But nice try!");
+            $this->path = $url;
         }
 
         return $this;
diff --git a/src/EntityListeners/AttachmentDeleteListener.php b/src/EntityListeners/AttachmentDeleteListener.php
new file mode 100644
index 00000000..239ef65e
--- /dev/null
+++ b/src/EntityListeners/AttachmentDeleteListener.php
@@ -0,0 +1,91 @@
+<?php
+/**
+ *
+ * part-db version 0.1
+ * Copyright (C) 2005 Christoph Lechner
+ * http://www.cl-projects.de/
+ *
+ * part-db version 0.2+
+ * Copyright (C) 2009 K. Jacobs and others (see authors.php)
+ * http://code.google.com/p/part-db/
+ *
+ * Part-DB Version 0.4+
+ * Copyright (C) 2016 - 2019 Jan Böhmer
+ * https://github.com/jbtronics
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
+ *
+ */
+
+namespace App\EntityListeners;
+
+
+use App\Entity\Attachments\Attachment;
+use App\Services\AttachmentHelper;
+use App\Services\AttachmentReverseSearch;
+use Doctrine\ORM\Event\LifecycleEventArgs;
+use Doctrine\ORM\Event\PreUpdateEventArgs;
+use Doctrine\ORM\Mapping\PostRemove;
+use Doctrine\ORM\Mapping\PreUpdate;
+
+/**
+ * This listener watches for changes on attachments and deletes the files associated with an attachment, that are not
+ * used any more. This can happens after an attachment is delteted or the path is changed.
+ * @package App\EntityListeners
+ */
+class AttachmentDeleteListener
+{
+    protected $attachmentReverseSearch;
+    protected $attachmentHelper;
+
+    public function __construct(AttachmentReverseSearch $attachmentReverseSearch, AttachmentHelper $attachmentHelper)
+    {
+        $this->attachmentReverseSearch = $attachmentReverseSearch;
+        $this->attachmentHelper = $attachmentHelper;
+    }
+
+    /**
+     * Removes the file associated with the attachment, if the file associated with the attachment changes.
+     * @param Attachment $attachment
+     * @param PreUpdateEventArgs $event
+     *
+     * @PreUpdate
+     */
+    public function preUpdateHandler(Attachment $attachment, PreUpdateEventArgs $event)
+    {
+        if ($event->hasChangedField('path')) {
+            $file = new \SplFileInfo($this->attachmentHelper->placeholderToRealPath($event->getOldValue('path')));
+            $this->attachmentReverseSearch->deleteIfNotUsed($file);
+        }
+    }
+
+    /**
+     * Removes the file associated with the attachment, after the attachment was deleted.
+     *
+     * @param Attachment $attachment
+     * @param LifecycleEventArgs $event
+     *
+     * @PostRemove
+     */
+    public function postRemoveHandler(Attachment $attachment, LifecycleEventArgs $event)
+    {
+        $file = $this->attachmentHelper->attachmentToFile($attachment);
+        //Only delete if the attachment has a valid file.
+        if ($file !== null) {
+            $this->attachmentReverseSearch->deleteIfNotUsed($file);
+        }
+    }
+
+}
\ No newline at end of file
diff --git a/src/Services/AttachmentHelper.php b/src/Services/AttachmentHelper.php
index 3530da19..ae8ac403 100644
--- a/src/Services/AttachmentHelper.php
+++ b/src/Services/AttachmentHelper.php
@@ -34,10 +34,8 @@ namespace App\Services;
 
 use App\Entity\Attachments\Attachment;
 use App\Entity\Attachments\PartAttachment;
-use Doctrine\ORM\EntityManagerInterface;
 use Symfony\Component\DependencyInjection\ParameterBag\ParameterBagInterface;
 use Symfony\Component\Filesystem\Filesystem;
-use Symfony\Component\HttpFoundation\File\File;
 use Symfony\Component\HttpFoundation\File\UploadedFile;
 use Symfony\Component\HttpKernel\KernelInterface;
 
@@ -71,6 +69,21 @@ class AttachmentHelper
         return $this->base_path;
     }
 
+    /**
+     * Gets an SPLFileInfo object representing the file associated with the attachment.
+     * @param Attachment $attachment The attachment for which the file should be generated
+     * @return \SplFileInfo|null The fileinfo for the attachment file. Null, if the attachment is external or has
+     * invalid file.
+     */
+    public function attachmentToFile(Attachment $attachment) : ?\SplFileInfo
+    {
+        if ($attachment->isExternal() || !$this->isFileExisting($attachment)) {
+            return null;
+        }
+
+        return new \SplFileInfo($this->toAbsoluteFilePath($attachment));
+    }
+
     /**
      * Converts an relative placeholder filepath (with %MEDIA% or older %BASE%) to an absolute filepath on disk.
      * @param string $placeholder_path The filepath with placeholder for which the real path should be determined.
diff --git a/src/Services/AttachmentReverseSearch.php b/src/Services/AttachmentReverseSearch.php
index 3d69d303..d80ac220 100644
--- a/src/Services/AttachmentReverseSearch.php
+++ b/src/Services/AttachmentReverseSearch.php
@@ -33,6 +33,7 @@ namespace App\Services;
 
 use App\Entity\Attachments\Attachment;
 use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Component\Filesystem\Filesystem;
 use Symfony\Component\HttpFoundation\File\File;
 
 /**
@@ -66,4 +67,22 @@ class AttachmentReverseSearch
         return $repo->findBy(['path' => [$relative_path_new, $relative_path_old]]);
     }
 
+    /**
+     * Deletes the given file if it is not used by more than $threshold attachments
+     * @param \SplFileInfo $file The file that should be removed
+     * @param int $threshold The threshold used, to determine if a file should be deleted or not.
+     * @return bool True, if the file was delete. False if not.
+     */
+    public function deleteIfNotUsed(\SplFileInfo $file, int $threshold = 0) : bool
+    {
+        /* When the file is used more then $threshold times, don't delete it */
+        if (count($this->findAttachmentsByFile($file)) > $threshold) {
+            return false;
+        }
+
+        $fs = new Filesystem();
+        $fs->remove($file);
+
+        return true;
+    }
 }
\ No newline at end of file