diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -1062,6 +1062,7 @@
     'PasteCreateConduitAPIMethod' => 'applications/paste/conduit/PasteCreateConduitAPIMethod.php',
     'PasteCreateMailReceiver' => 'applications/paste/mail/PasteCreateMailReceiver.php',
     'PasteDefaultViewCapability' => 'applications/paste/capability/PasteDefaultViewCapability.php',
+    'PasteEditConduitAPIMethod' => 'applications/paste/conduit/PasteEditConduitAPIMethod.php',
     'PasteEmbedView' => 'applications/paste/view/PasteEmbedView.php',
     'PasteInfoConduitAPIMethod' => 'applications/paste/conduit/PasteInfoConduitAPIMethod.php',
     'PasteMockMailReceiver' => 'applications/paste/mail/PasteMockMailReceiver.php',
@@ -3851,6 +3852,7 @@
     'PasteCreateConduitAPIMethod' => 'PasteConduitAPIMethod',
     'PasteCreateMailReceiver' => 'PhabricatorMailReceiver',
     'PasteDefaultViewCapability' => 'PhabricatorPolicyCapability',
+    'PasteEditConduitAPIMethod' => 'PasteConduitAPIMethod',
     'PasteEmbedView' => 'AphrontView',
     'PasteInfoConduitAPIMethod' => 'PasteConduitAPIMethod',
     'PasteMockMailReceiver' => 'PhabricatorObjectMailReceiver',
diff --git a/src/applications/paste/conduit/PasteEditConduitAPIMethod.php b/src/applications/paste/conduit/PasteEditConduitAPIMethod.php
new file mode 100644
--- /dev/null
+++ b/src/applications/paste/conduit/PasteEditConduitAPIMethod.php
@@ -0,0 +1,102 @@
+<?php
+
+final class PasteEditConduitAPIMethod extends PasteConduitAPIMethod {
+
+  public function getAPIMethodName() {
+    return 'paste.edit';
+  }
+
+  public function getMethodDescription() {
+    return 'Edit a paste.';
+  }
+
+  public function defineParamTypes() {
+    return array(
+      'content'   => 'required string',
+      'paste_id'  => 'required id',
+      'title'     => 'optional string',
+      'language'  => 'optional string',
+    );
+  }
+
+  public function defineReturnType() {
+    return 'nonempty dict';
+  }
+
+  public function defineErrorTypes() {
+    return array(
+      'ERR-NO-PASTE' => 'Paste may not be empty.',
+      'ERR-NO-ACCESS' => 'You do not have permission to edit this paste.',
+      'ERR-BAD-PASTE' => 'No such paste exists',
+    );
+  }
+
+  protected function execute(ConduitAPIRequest $request) {
+    $content  = $request->getValue('content');
+    $title    = $request->getValue('title');
+    $language = $request->getValue('language');
+    $paste_id = $request->getValue('paste_id');
+
+    if (!strlen($content)) {
+      throw new ConduitException('ERR-NO-PASTE');
+    }
+
+    $viewer = $request->getUser();
+
+    try {
+        $paste = id(new PhabricatorPasteQuery())
+            ->setViewer($request->getUser())
+            ->requireCapabilities(
+                array(
+                    PhabricatorPolicyCapability::CAN_VIEW,
+                    PhabricatorPolicyCapability::CAN_EDIT,
+                ))
+            ->withIDs(array($paste_id))
+            ->needRawContent(true)
+            ->executeOne();
+    } catch (PhabricatorPolicyException $ex) {
+        throw new ConduitException('ERR-NO-ACCESS');
+    }
+
+    if (!$paste) {
+        throw new ConduitException('ERR-BAD-PASTE');
+    }
+
+    $xactions = array();
+
+    if ($content != $paste->getRawContent()) {
+        $file = PhabricatorPasteEditor::initializeFileForPaste(
+          $viewer,
+          $title,
+          $content);
+
+        $xactions[] = id(new PhabricatorPasteTransaction())
+          ->setTransactionType(PhabricatorPasteTransaction::TYPE_CONTENT)
+          ->setNewValue($file->getPHID());
+    }
+
+    if ($title && $title != $paste->getTitle()) {
+        $xactions[] = id(new PhabricatorPasteTransaction())
+          ->setTransactionType(PhabricatorPasteTransaction::TYPE_TITLE)
+          ->setNewValue($title);
+    }
+
+    if ($language && $language != $paste->getLanguage()) {
+        $xactions[] = id(new PhabricatorPasteTransaction())
+          ->setTransactionType(PhabricatorPasteTransaction::TYPE_LANGUAGE)
+          ->setNewValue($language);
+    }
+
+    if (count($xactions) > 0) {
+        $editor = id(new PhabricatorPasteEditor())
+          ->setActor($viewer)
+          ->setContentSourceFromConduitRequest($request);
+
+        $xactions = $editor->applyTransactions($paste, $xactions);
+
+        $paste->attachRawContent($content);
+    }
+    return $this->buildPasteInfoDictionary($paste);
+  }
+
+}