diff --git a/apps/dav/lib/CalDAV/CalDavBackend.php b/apps/dav/lib/CalDAV/CalDavBackend.php
index 88ee778e82..14de848013 100644
--- a/apps/dav/lib/CalDAV/CalDavBackend.php
+++ b/apps/dav/lib/CalDAV/CalDavBackend.php
@@ -12,6 +12,8 @@
  * @author Stefan Weil <sw@weilnetz.de>
  * @author Thomas Citharel <tcit@tcit.fr>
  * @author Thomas Müller <thomas.mueller@tmit.eu>
+ * @author Vinicius Cubas Brand <vinicius@eita.org.br>
+ * @author Daniel Tygel <dtygel@eita.org.br>
  *
  * @license AGPL-3.0
  *
@@ -301,6 +303,8 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 
 		// query for shared calendars
 		$principals = $this->principalBackend->getGroupMembership($principalUriOriginal, true);
+		$principals = array_merge($principals, $this->principalBackend->getCircleMembership($principalUriOriginal));
+
 		$principals = array_map(function($principal) {
 			return urldecode($principal);
 		}, $principals);
diff --git a/apps/dav/lib/Connector/Sabre/Principal.php b/apps/dav/lib/Connector/Sabre/Principal.php
index 2574fbcd43..39b4da683a 100644
--- a/apps/dav/lib/Connector/Sabre/Principal.php
+++ b/apps/dav/lib/Connector/Sabre/Principal.php
@@ -13,6 +13,8 @@
  * @author Thomas Tanghus <thomas@tanghus.net>
  * @author Vincent Petry <pvince81@owncloud.com>
  * @author Georg Ehrke <oc.list@georgehrke.com>
+ * @author Vinicius Cubas Brand <vinicius@eita.org.br>
+ * @author Daniel Tygel <dtygel@eita.org.br>
  *
  * @license AGPL-3.0
  *
@@ -66,6 +68,9 @@ class Principal implements BackendInterface {
 	/** @var bool */
 	private $hasGroups;
 
+	/** @var bool */
+	private $hasCircles;
+
 	/**
 	 * @param IUserManager $userManager
 	 * @param IGroupManager $groupManager
@@ -86,7 +91,7 @@ class Principal implements BackendInterface {
 		$this->userSession = $userSession;
 		$this->config = $config;
 		$this->principalPrefix = trim($principalPrefix, '/');
-		$this->hasGroups = ($principalPrefix === 'principals/users/');
+		$this->hasGroups = $this->hasCircles = ($principalPrefix === 'principals/users/');
 	}
 
 	/**
@@ -131,6 +136,8 @@ class Principal implements BackendInterface {
 			if ($user !== null) {
 				return $this->userToPrincipal($user);
 			}
+		} else if ($prefix === 'principals/circles') {
+			return $this->circleToPrincipal($name);
 		}
 		return null;
 	}
@@ -388,4 +395,66 @@ class Principal implements BackendInterface {
 		return $this->principalPrefix;
 	}
 
+	/**
+	 * @param string $circleUniqueId
+	 * @return array|null
+	 */
+	protected function circleToPrincipal($circleUniqueId) {
+		if (!\OC::$server->getAppManager()->isEnabledForUser('circles') || !class_exists('\OCA\Circles\ShareByCircleProvider')) {
+			return null;
+		}
+
+		$circle = \OCA\Circles\Api\v1\Circles::detailsCircle($circleUniqueId);
+
+		if (!$circle) {
+			return null;
+		}
+
+		$principal = [
+			'uri' => 'principals/circles/' . $circleUniqueId,
+			'{DAV:}displayname' => $circle->getName(),
+		];
+
+		return $principal;
+	}
+
+	/**
+	 * Returns the list of circles a principal is a member of
+	 *
+	 * @param string $principal
+	 * @param bool $needGroups
+	 * @return array
+	 * @throws Exception
+	 */
+	public function getCircleMembership($principal) {
+		if (!\OC::$server->getAppManager()->isEnabledForUser('circles') || !class_exists('\OCA\Circles\ShareByCircleProvider')) {
+			return [];
+		}
+
+		list($prefix, $name) = \Sabre\Uri\split($principal);
+
+		if ($this->hasCircles && $prefix === $this->principalPrefix) {
+			$user = $this->userManager->get($name);
+			if (!$user) {
+				throw new Exception('Principal not found');
+			}
+
+			$userSession = \OC::$server->getUserSession();
+			$currentUser = $userSession->getUser();
+
+			$userSession->setUser($user);
+			$circles = \OCA\Circles\Api\v1\Circles::joinedCircles();
+			$userSession->setUser($currentUser);
+
+			$circles = array_map(function($circle) {
+				/** @var \OCA\Circles\Model\Circle $group */
+				return 'principals/circles/' . urlencode($circle->getUniqueId());
+			}, $circles);
+
+			return $circles;
+
+		}
+		return [];
+	}
+
 }
diff --git a/apps/dav/lib/Connector/Sabre/SharesPlugin.php b/apps/dav/lib/Connector/Sabre/SharesPlugin.php
index 990cc4a808..46174c8118 100644
--- a/apps/dav/lib/Connector/Sabre/SharesPlugin.php
+++ b/apps/dav/lib/Connector/Sabre/SharesPlugin.php
@@ -7,6 +7,8 @@
  * @author Robin Appelman <robin@icewind.nl>
  * @author Roeland Jago Douma <roeland@famdouma.nl>
  * @author Vincent Petry <pvince81@owncloud.com>
+ * @author Vinicius Cubas Brand <vinicius@eita.org.br>
+ * @author Daniel Tygel <dtygel@eita.org.br>
  *
  * @license AGPL-3.0
  *
@@ -125,6 +127,7 @@ class SharesPlugin extends \Sabre\DAV\ServerPlugin {
 			\OCP\Share::SHARE_TYPE_REMOTE,
 			\OCP\Share::SHARE_TYPE_EMAIL,
 			\OCP\Share::SHARE_TYPE_ROOM,
+			\OCP\Share::SHARE_TYPE_CIRCLE,
 		];
 		foreach ($requestedShareTypes as $requestedShareType) {
 			// one of each type is enough to find out about the types
diff --git a/apps/dav/lib/DAV/Sharing/Backend.php b/apps/dav/lib/DAV/Sharing/Backend.php
index 433d9db9c0..ebb63b41c9 100644
--- a/apps/dav/lib/DAV/Sharing/Backend.php
+++ b/apps/dav/lib/DAV/Sharing/Backend.php
@@ -99,7 +99,7 @@ class Backend {
 		}
 
 		$principal = explode('/', $parts[1], 3);
-		if (count($principal) !== 3 || $principal[0] !== 'principals' || !in_array($principal[1], ['users', 'groups'], true)) {
+		if (count($principal) !== 3 || $principal[0] !== 'principals' || !in_array($principal[1], ['users', 'groups','circles'], true)) {
 			// Invalid principal
 			return;
 		}