diff --git a/src/applications/maniphest/query/ManiphestTaskQuery.php b/src/applications/maniphest/query/ManiphestTaskQuery.php
--- a/src/applications/maniphest/query/ManiphestTaskQuery.php
+++ b/src/applications/maniphest/query/ManiphestTaskQuery.php
@@ -572,6 +572,8 @@
   }
 
   private function buildCustomOrderClause(AphrontDatabaseConnection $conn) {
+    $reverse = ($this->getBeforeID() xor $this->getReversePaging());
+
     $order = array();
 
     switch ($this->groupBy) {
@@ -593,33 +595,35 @@
         throw new Exception("Unknown group query '{$this->groupBy}'!");
     }
 
-    switch ($this->orderBy) {
-      case self::ORDER_PRIORITY:
-        $order[] = 'priority';
-        $order[] = 'subpriority';
-        $order[] = 'dateModified';
-        break;
-      case self::ORDER_CREATED:
-        $order[] = 'id';
-        break;
-      case self::ORDER_MODIFIED:
-        $order[] = 'dateModified';
-        break;
-      case self::ORDER_TITLE:
-        $order[] = 'title';
-        break;
-      default:
-        throw new Exception("Unknown order query '{$this->orderBy}'!");
+    $app_order = $this->buildApplicationSearchOrders($conn, $reverse);
+
+    if (!$app_order) {
+      switch ($this->orderBy) {
+        case self::ORDER_PRIORITY:
+          $order[] = 'priority';
+          $order[] = 'subpriority';
+          $order[] = 'dateModified';
+          break;
+        case self::ORDER_CREATED:
+          $order[] = 'id';
+          break;
+        case self::ORDER_MODIFIED:
+          $order[] = 'dateModified';
+          break;
+        case self::ORDER_TITLE:
+          $order[] = 'title';
+          break;
+        default:
+          throw new Exception("Unknown order query '{$this->orderBy}'!");
+      }
     }
 
     $order = array_unique($order);
 
-    if (empty($order)) {
+    if (empty($order) && empty($app_order)) {
       return null;
     }
 
-    $reverse = ($this->getBeforeID() xor $this->getReversePaging());
-
     foreach ($order as $k => $column) {
       switch ($column) {
         case 'subpriority':
@@ -653,6 +657,18 @@
       }
     }
 
+    if ($app_order) {
+      foreach ($app_order as $order_by) {
+        $order[] = $order_by;
+      }
+
+      if ($reverse) {
+        $order[] = 'task.id ASC';
+      } else {
+        $order[] = 'task.id DESC';
+      }
+    }
+
     return 'ORDER BY '.implode(', ', $order);
   }
 
@@ -903,55 +919,65 @@
         throw new Exception("Unknown group query '{$this->groupBy}'!");
     }
 
-    switch ($this->orderBy) {
-      case self::ORDER_PRIORITY:
-        if ($this->groupBy != self::GROUP_PRIORITY) {
+    $app_columns = $this->buildApplicationSearchPagination($conn_r, $cursor);
+    if ($app_columns) {
+      $columns = array_merge($columns, $app_columns);
+      $columns[] = array(
+        'name' => 'task.id',
+        'value' => (int)$cursor->getID(),
+        'type' => 'int',
+      );
+    } else {
+      switch ($this->orderBy) {
+        case self::ORDER_PRIORITY:
+          if ($this->groupBy != self::GROUP_PRIORITY) {
+            $columns[] = array(
+              'name' => 'task.priority',
+              'value' => (int)$cursor->getPriority(),
+              'type' => 'int',
+            );
+          }
           $columns[] = array(
-            'name' => 'task.priority',
-            'value' => (int)$cursor->getPriority(),
+            'name' => 'task.subpriority',
+            'value' => (int)$cursor->getSubpriority(),
             'type' => 'int',
+            'reverse' => true,
           );
-        }
-        $columns[] = array(
-          'name' => 'task.subpriority',
-          'value' => (int)$cursor->getSubpriority(),
-          'type' => 'int',
-          'reverse' => true,
-        );
-        $columns[] = array(
-          'name' => 'task.dateModified',
-          'value' => (int)$cursor->getDateModified(),
-          'type' => 'int',
-        );
-        break;
-      case self::ORDER_CREATED:
-        $columns[] = array(
-          'name' => 'task.id',
-          'value' => (int)$cursor->getID(),
-          'type' => 'int',
-        );
-        break;
-      case self::ORDER_MODIFIED:
-        $columns[] = array(
-          'name' => 'task.dateModified',
-          'value' => (int)$cursor->getDateModified(),
-          'type' => 'int',
-        );
-        break;
-      case self::ORDER_TITLE:
-        $columns[] = array(
-          'name' => 'task.title',
-          'value' => $cursor->getTitle(),
-          'type' => 'string',
-        );
-        $columns[] = array(
-          'name' => 'task.id',
-          'value' => $cursor->getID(),
-          'type' => 'int',
-        );
-        break;
-      default:
-        throw new Exception("Unknown order query '{$this->orderBy}'!");
+          $columns[] = array(
+            'name' => 'task.dateModified',
+            'value' => (int)$cursor->getDateModified(),
+            'type' => 'int',
+          );
+          break;
+        case self::ORDER_CREATED:
+          $columns[] = array(
+            'name' => 'task.id',
+            'value' => (int)$cursor->getID(),
+            'type' => 'int',
+          );
+          break;
+        case self::ORDER_MODIFIED:
+          $columns[] = array(
+            'name' => 'task.dateModified',
+            'value' => (int)$cursor->getDateModified(),
+            'type' => 'int',
+          );
+          break;
+        case self::ORDER_TITLE:
+          $columns[] = array(
+            'name' => 'task.title',
+            'value' => $cursor->getTitle(),
+            'type' => 'string',
+          );
+          $columns[] = array(
+            'name' => 'task.id',
+            'value' => $cursor->getID(),
+            'type' => 'int',
+          );
+          break;
+        default:
+          throw new Exception("Unknown order query '{$this->orderBy}'!");
+      }
     }
 
     return $this->buildPagingClauseFromMultipleColumns(
diff --git a/src/applications/maniphest/query/ManiphestTaskSearchEngine.php b/src/applications/maniphest/query/ManiphestTaskSearchEngine.php
--- a/src/applications/maniphest/query/ManiphestTaskSearchEngine.php
+++ b/src/applications/maniphest/query/ManiphestTaskSearchEngine.php
@@ -151,13 +151,10 @@
       $query->withPriorities($priorities);
     }
 
-    $order = $saved->getParameter('order');
-    $order = idx($this->getOrderValues(), $order);
-    if ($order) {
-      $query->setOrderBy($order);
-    } else {
-      $query->setOrderBy(head($this->getOrderValues()));
-    }
+    $this->applyOrderByToQuery(
+      $query,
+      $this->getOrderValues(),
+      $saved->getParameter('order'));
 
     $group = $saved->getParameter('group');
     $group = idx($this->getGroupValues(), $group);
@@ -306,6 +303,10 @@
 
     $ids = $saved->getParameter('ids', array());
 
+    $builtin_orders = $this->getOrderOptions();
+    $custom_orders = $this->getCustomFieldOrderOptions();
+    $all_orders = $builtin_orders + $custom_orders;
+
     $form
       ->appendChild(
         id(new AphrontFormTokenizerControl())
@@ -385,7 +386,7 @@
             ->setName('order')
             ->setLabel(pht('Order By'))
             ->setValue($saved->getParameter('order'))
-            ->setOptions($this->getOrderOptions()));
+            ->setOptions($all_orders));
     }
 
     $form
diff --git a/src/applications/search/engine/PhabricatorApplicationSearchEngine.php b/src/applications/search/engine/PhabricatorApplicationSearchEngine.php
--- a/src/applications/search/engine/PhabricatorApplicationSearchEngine.php
+++ b/src/applications/search/engine/PhabricatorApplicationSearchEngine.php
@@ -764,6 +764,65 @@
     }
   }
 
+  protected function applyOrderByToQuery(
+    PhabricatorCursorPagedPolicyAwareQuery $query,
+    array $standard_values,
+    $order) {
+
+    if (substr($order, 0, 7) === 'custom:') {
+      $list = $this->getCustomFieldList();
+      if (!$list) {
+        $query->setOrderBy(head($standard_values));
+        return;
+      }
+
+      foreach ($list->getFields() as $field) {
+        $key = $this->getKeyForCustomField($field);
+
+        if ($key === $order) {
+          $index = $field->buildOrderIndex();
+
+          if ($index === null) {
+            $query->setOrderBy(head($standard_values));
+            return;
+          }
+
+          $query->withApplicationSearchOrder(
+            $field,
+            $index,
+            false);
+          break;
+        }
+      }
+    } else {
+      $order = idx($standard_values, $order);
+      if ($order) {
+        $query->setOrderBy($order);
+      } else {
+        $query->setOrderBy(head($standard_values));
+      }
+    }
+  }
+
+
+  protected function getCustomFieldOrderOptions() {
+    $list = $this->getCustomFieldList();
+    if (!$list) {
+      return;
+    }
+
+    $custom_order = array();
+    foreach ($list->getFields() as $field) {
+      if ($field->shouldAppearInApplicationSearch()) {
+        if ($field->buildOrderIndex() !== null) {
+          $key = $this->getKeyForCustomField($field);
+          $custom_order[$key] = $field->getFieldName();
+        }
+      }
+    }
+
+    return $custom_order;
+  }
 
   /**
    * Get a unique key identifying a field.
diff --git a/src/infrastructure/customfield/field/PhabricatorCustomField.php b/src/infrastructure/customfield/field/PhabricatorCustomField.php
--- a/src/infrastructure/customfield/field/PhabricatorCustomField.php
+++ b/src/infrastructure/customfield/field/PhabricatorCustomField.php
@@ -621,6 +621,28 @@
 
 
   /**
+   * Return an index against which this field can be meaningfully ordered
+   * against to implement ApplicationSearch.
+   *
+   * This should be a single index, normally built using
+   * @{method:newStringIndex} and @{method:newNumericIndex}.
+   *
+   * The value of the index is not used.
+   *
+   * Return null from this method if the field can not be ordered.
+   *
+   * @return PhabricatorCustomFieldIndexStorage A single index to order by.
+   * @task appsearch
+   */
+  public function buildOrderIndex() {
+    if ($this->proxy) {
+      return $this->proxy->buildOrderIndex();
+    }
+    return null;
+  }
+
+
+  /**
    * Build a new empty storage object for storing string indexes. Normally,
    * this should be a concrete subclass of
    * @{class:PhabricatorCustomFieldStringIndexStorage}.
diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomField.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomField.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomField.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomField.php
@@ -260,6 +260,10 @@
     return array();
   }
 
+  public function buildOrderIndex() {
+    return null;
+  }
+
   public function readApplicationSearchValueFromRequest(
     PhabricatorApplicationSearchEngine $engine,
     AphrontRequest $request) {
diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldBool.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldBool.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldBool.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldBool.php
@@ -18,6 +18,10 @@
     return $indexes;
   }
 
+  public function buildOrderIndex() {
+    return $this->newNumericIndex(0);
+  }
+
   public function getValueForStorage() {
     $value = $this->getFieldValue();
     if (strlen($value)) {
diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldDate.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldDate.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldDate.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldDate.php
@@ -18,6 +18,10 @@
     return $indexes;
   }
 
+  public function buildOrderIndex() {
+    return $this->newNumericIndex(0);
+  }
+
   public function getValueForStorage() {
     $value = $this->getFieldValue();
     if (strlen($value)) {
diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldInt.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldInt.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldInt.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldInt.php
@@ -18,6 +18,10 @@
     return $indexes;
   }
 
+  public function buildOrderIndex() {
+    return $this->newNumericIndex(0);
+  }
+
   public function getValueForStorage() {
     $value = $this->getFieldValue();
     if (strlen($value)) {
diff --git a/src/infrastructure/query/policy/PhabricatorCursorPagedPolicyAwareQuery.php b/src/infrastructure/query/policy/PhabricatorCursorPagedPolicyAwareQuery.php
--- a/src/infrastructure/query/policy/PhabricatorCursorPagedPolicyAwareQuery.php
+++ b/src/infrastructure/query/policy/PhabricatorCursorPagedPolicyAwareQuery.php
@@ -12,6 +12,7 @@
   private $afterID;
   private $beforeID;
   private $applicationSearchConstraints = array();
+  private $applicationSearchOrders = array();
   private $internalPaging;
 
   protected function getPagingColumn() {
@@ -360,6 +361,32 @@
 
 
   /**
+   * Order the results by an ApplicationSearch index.
+   *
+   * @param PhabricatorCustomField Field to which the index belongs.
+   * @param PhabricatorCustomFieldIndexStorage Table where the index is stored.
+   * @param bool True to sort ascending.
+   * @return this
+   * @task appsearch
+   */
+  public function withApplicationSearchOrder(
+    PhabricatorCustomField $field,
+    PhabricatorCustomFieldIndexStorage $index,
+    $ascending) {
+
+    $this->applicationSearchOrders[] = array(
+      'key' => $field->getFieldKey(),
+      'type' => $index->getIndexValueType(),
+      'table' => $index->getTableName(),
+      'index' => $index->getIndexKey(),
+      'ascending' => $ascending,
+    );
+
+    return $this;
+  }
+
+
+  /**
    * Get the name of the query's primary object PHID column, for constructing
    * JOIN clauses. Normally (and by default) this is just `"phid"`, but if the
    * query construction requires a table alias it may be something like
@@ -535,7 +562,72 @@
       }
     }
 
+    foreach ($this->applicationSearchOrders as $key => $order) {
+      $table = $order['table'];
+      $alias = 'appsearch_order_'.$key;
+      $index = $order['index'];
+      $phid_column = $this->getApplicationSearchObjectPHIDColumn();
+
+      $joins[] = qsprintf(
+        $conn_r,
+        'JOIN %T %T ON %T.objectPHID = %Q
+          AND %T.indexKey = %s',
+        $table,
+        $alias,
+        $alias,
+        $phid_column,
+        $alias,
+        $index);
+    }
+
     return implode(' ', $joins);
   }
 
+  protected function buildApplicationSearchOrders(
+    AphrontDatabaseConnection $conn_r,
+    $reverse) {
+
+    $orders = array();
+    foreach ($this->applicationSearchOrders as $key => $order) {
+      $alias = 'appsearch_order_'.$key;
+
+      if ($order['ascending'] xor $reverse) {
+        $orders[] = qsprintf($conn_r, '%T.indexValue ASC', $alias);
+      } else {
+        $orders[] = qsprintf($conn_r, '%T.indexValue DESC', $alias);
+      }
+    }
+
+    return $orders;
+  }
+
+  protected function buildApplicationSearchPagination(
+    AphrontDatabaseConnection $conn_r,
+    $cursor) {
+
+    // We have to get the current field values on the cursor object.
+    $fields = PhabricatorCustomField::getObjectFields(
+      $cursor,
+      PhabricatorCustomField::ROLE_APPLICATIONSEARCH);
+    $fields->setViewer($this->getViewer());
+    $fields->readFieldsFromStorage($cursor);
+
+    $fields = mpull($fields->getFields(), null, 'getFieldKey');
+
+    $columns = array();
+    foreach ($this->applicationSearchOrders as $key => $order) {
+      $alias = 'appsearch_order_'.$key;
+
+      $field = idx($fields, $order['key']);
+
+      $columns[] = array(
+        'name' => $alias.'.indexValue',
+        'value' => $field->getValueForStorage(),
+        'type' => $order['type'],
+      );
+    }
+
+    return $columns;
+  }
+
 }