diff --git a/app/assets/javascripts/artist_commentaries.js b/app/assets/javascripts/artist_commentaries.js
index 44845c697..6e3b0a5ee 100644
--- a/app/assets/javascripts/artist_commentaries.js
+++ b/app/assets/javascripts/artist_commentaries.js
@@ -53,6 +53,91 @@
       e.preventDefault();
       $("#add-commentary-dialog").dialog("open");
     });
+
+    $('#fetch-commentary select[name="commentary_source_type"]').change(function() {
+      $("#fetch-commentary input").toggle();
+    });
+
+    $('#fetch-commentary button[type="submit"]').click(Danbooru.ArtistCommentary.fetch_commentary);
+  }
+
+  Danbooru.ArtistCommentary.fetch_commentary = function() {
+    Danbooru.notice("Fetching artist commentary...");
+
+    var type = $('#fetch-commentary select[name="commentary_source_type"]').val();
+    if (type === "Source") {
+      var source = $('#fetch-commentary input[name="commentary_source"]').val();
+      var commentary = Danbooru.ArtistCommentary.from_source(source);
+    } else if (type === "Post") {
+      var id = $('#fetch-commentary input[name="commentary_post_id"]').val();
+      var commentary = Danbooru.ArtistCommentary.from_post_id(id);
+    }
+
+    commentary.then(Danbooru.ArtistCommentary.fill_commentary).done(function (success) {
+      var message = success ? "Artist commentary copied." : "Artist commentary copied; conflicting fields ignored.";
+      Danbooru.notice(message);
+    }).fail(function () {
+      Danbooru.notice("Fetching artist commentary failed.");
+    });
+
+    return false;
+  };
+
+  Danbooru.ArtistCommentary.from_source = function(source) {
+    return $.get("/source.json?url=" + encodeURIComponent(source)).then(function(data) {
+      return {
+        original_title: data.artist_commentary.title,
+        original_description: data.artist_commentary.description,
+        source: source,
+      };
+    });
+  };
+
+  Danbooru.ArtistCommentary.from_post_id = function(post_id) {
+    return $.get("/posts/" + encodeURIComponent(post_id) + "/artist_commentary.json").then(function(commentary) {
+      commentary.source = "post #" + post_id;
+      return commentary;
+    });
+  };
+
+  Danbooru.ArtistCommentary.fill_commentary = function(commentary) {
+    var description = Danbooru.ArtistCommentary.merge_commentaries($("#artist_commentary_original_description").val().trim(), commentary);
+    $("#artist_commentary_original_description").val(description);
+
+    // Update the other fields if they're blank. Return success if none conflict.
+    return [
+      Danbooru.ArtistCommentary.update_field($("#artist_commentary_original_title"), commentary.original_title),
+      Danbooru.ArtistCommentary.update_field($("#artist_commentary_translated_title"), commentary.translated_title),
+      Danbooru.ArtistCommentary.update_field($("#artist_commentary_translated_description"), commentary.translated_description),
+    ].every(function (i) { return i; });
+  };
+
+  // If the new description conflicts with the current description, merge them
+  // by appending the new description onto the old one.
+  Danbooru.ArtistCommentary.merge_commentaries = function(description, commentary) {
+    if ((commentary.original_description && description) &&
+        (commentary.original_description != description)) {
+      return description
+        + "\n\n[tn]\nSource: " + $("#post_source").val() + "\n[/tn]"
+        + "\n\nh6. " + (commentary.original_title || "Untitled")
+        + "\n\n" + commentary.original_description
+        + "\n\n[tn]\nSource: " + commentary.source + "\n[/tn]";
+    } else  {
+      return commentary.original_description || description;
+    }
+  };
+
+  // Update commentary field if it's blank, signal an error if there's a conflict.
+  Danbooru.ArtistCommentary.update_field = function($field, value) {
+    if ($field.val().trim() === "") {
+      $field.val(value);
+      return true;
+    } else if ($field.val().trim() !== value) {
+      $field.effect("shake", { direction: "up", distance: 5 });
+      return false;
+    } else {
+      return true;
+    }
   }
 })();
 
diff --git a/app/views/artist_commentaries/_form.html.erb b/app/views/artist_commentaries/_form.html.erb
index b173e342e..0c7fd6e02 100644
--- a/app/views/artist_commentaries/_form.html.erb
+++ b/app/views/artist_commentaries/_form.html.erb
@@ -1,5 +1,15 @@
 <p>If the artist of this image posted some interesting additional information about this work, you can copy it here. <%= link_to "View help.", wiki_pages_path(:search => {:title => "help:artist_commentary"}) %></p>
 
+<form id="fetch-commentary" class="simple_form">
+  <div class="input">
+    <label>Copy from</label>
+    <%= select_tag :commentary_source_type, options_for_select(%w[Source Post]) %>
+    <%= text_field_tag :commentary_source, @post.source %>
+    <%= text_field_tag :commentary_post_id, (@post.parent.try(&:id) || @post.children.first.try(&:id)), :style => "display: none;" %>
+    <%= button_tag "Fetch" %>
+  </div>
+</form>
+
 <%= form_tag(create_or_update_artist_commentaries_path(:format => :js), :remote => true, :class => "simple_form", :method => :put) do %>
   <%= hidden_field :artist_commentary, :post_id, :value => @post.id %>