diff --git a/src/applications/project/engine/PhabricatorProjectEditEngine.php b/src/applications/project/engine/PhabricatorProjectEditEngine.php
--- a/src/applications/project/engine/PhabricatorProjectEditEngine.php
+++ b/src/applications/project/engine/PhabricatorProjectEditEngine.php
@@ -128,6 +128,19 @@
         if (isset($unavailable[$xaction_type])) {
           unset($fields[$key]);
         }
+        // Paste previous milestone description as default when creating next
+        if ($this->getIsCreate() &&
+            $field instanceof PhabricatorCustomFieldEditField &&
+            $field->getLabel() === 'Description' ) {
+          $default_desc_text = $this->getPreviousMilestoneDescription();
+          if (phutil_nonempty_string($default_desc_text)) {
+            $field->setValue($default_desc_text);
+            $field->setControlInstructions(
+              pht('Description text below was copied from the previous '.
+              'milestone for convenience. Please update/remove the text.'));
+          }
+          break;
+        }
       }
     }
 
@@ -320,7 +333,44 @@
     }
 
     return $fields;
+  }
 
+  /**
+   * Get the description of the previous milestone project in the series
+   * @return string|null Description text of previous milestone
+   */
+  private function getPreviousMilestoneDescription() {
+    $milestone = $this->getMilestoneProject();
+    if ($milestone) {
+      $number = ($milestone->loadNextMilestoneNumber() - 1);
+      if ($number > 0) {
+        $previous_milestone = id(new PhabricatorProjectQuery())
+          ->setViewer($this->getViewer())
+          ->withParentProjectPHIDs(array($milestone->getPHID()))
+          ->withIsMilestone(true)
+          ->withMilestoneNumberBetween($number, $number)
+          ->executeOne();
+        if ($previous_milestone) {
+          $desc_field = PhabricatorCustomField::getObjectField(
+            $previous_milestone,
+            PhabricatorCustomField::ROLE_VIEW,
+            'std:project:internal:description');
+          if ($desc_field) {
+            $viewer = $this->getViewer();
+            $desc_field
+              ->setViewer($viewer)
+              ->readValueFromObject($previous_milestone);
+            id(new PhabricatorCustomFieldStorageQuery())
+              ->addField($desc_field)
+              ->execute();
+            if (phutil_nonempty_string($desc_field->getValueForStorage())) {
+              return $desc_field->getValueForStorage();
+            }
+          }
+        }
+      }
+    }
+    return null;
   }
 
 }