diff --git a/app/assets/javascripts/app/controllers/ticket_zoom/sidebar_article_attachments.coffee b/app/assets/javascripts/app/controllers/ticket_zoom/sidebar_article_attachments.coffee
index 728cc00fb..743cb38ac 100644
--- a/app/assets/javascripts/app/controllers/ticket_zoom/sidebar_article_attachments.coffee
+++ b/app/assets/javascripts/app/controllers/ticket_zoom/sidebar_article_attachments.coffee
@@ -16,17 +16,36 @@ class SidebarArticleAttachments extends App.Controller
     if _.isEmpty(@ticket) || _.isEmpty(@ticket.article_ids)
       @el.html("<div>#{App.i18n.translateInline('none')}</div>")
       return
-    html = ''
-    for ticket_article_id in @ticket.article_ids.sort((a, b) -> b - a)
-      if App.TicketArticle.exists(ticket_article_id)
-        article = App.TicketArticle.find(ticket_article_id)
-        attachments = App.TicketArticle.contentAttachments(article)
-        if !_.isEmpty(attachments)
-          html += App.view('ticket_zoom/sidebar_article_attachment')(article: article, attachments: attachments)
+
+    articleIDs = _.clone(@ticket.article_ids)
+    articleIDs.sort((a, b) -> a - b)
+
+    uniqueAttachments = {}
+    ticketAttachments = []
+    for articleID in articleIDs
+      continue if !App.TicketArticle.exists(articleID)
+
+      article = App.TicketArticle.find(articleID)
+      attachments = App.TicketArticle.contentAttachments(article)
+      for attachment in attachments
+        continue if uniqueAttachments[attachment.store_file_id]
+        uniqueAttachments[attachment.store_file_id] = true
+
+        ticketAttachments.push({ attachment: attachment, article: article })
+
+    ticketAttachments = ticketAttachments.reverse()
+
+    html = App.view('ticket_zoom/sidebar_article_attachment')(
+      ticketAttachments: ticketAttachments,
+    )
+
     @el.html(html)
     @el.on('click', '.js-attachments img', (e) =>
       @imageView(e)
     )
+    @controllerBind('ui::ticket::load', =>
+      @showObjects(el)
+    )
 
   imageView: (e) ->
     e.preventDefault()
diff --git a/app/assets/javascripts/app/views/ticket_zoom/sidebar_article_attachment.jst.eco b/app/assets/javascripts/app/views/ticket_zoom/sidebar_article_attachment.jst.eco
index b8bf35a33..18927c739 100644
--- a/app/assets/javascripts/app/views/ticket_zoom/sidebar_article_attachment.jst.eco
+++ b/app/assets/javascripts/app/views/ticket_zoom/sidebar_article_attachment.jst.eco
@@ -1,12 +1,11 @@
 <div class="attachments-block js-attachments">
-  <div class="attachments-block-headline"><%- @humanTime(@article.created_at) %></div>
-  <% for attachment in @article.attachments: %>
-    <% content_type = @ContentOrMimeType(attachment) %>
-    <a class="attachment attachment--preview" title="<%- content_type %>" target="_blank" href="<%= App.Config.get('api_path') %>/ticket_attachment/<%= @article.ticket_id %>/<%= @article.id %>/<%= attachment.id %>?disposition=attachment" data-type="attachment"<% if @canDownload(content_type): %> download<% end %>>
+  <% for data in @ticketAttachments: %>
+    <% content_type = @ContentOrMimeType(data.attachment) %>
+    <a class="attachment attachment--preview" target="_blank" href="<%= App.Config.get('api_path') %>/ticket_attachment/<%= data.article.ticket_id %>/<%= data.article.id %>/<%= data.attachment.id %>?disposition=attachment" data-type="attachment"<% if @canDownload(content_type): %> download<% end %>>
       <div class="attachment-icon">
       <% if content_type && @ContentTypeIcon(content_type): %>
         <% if @canPreview(content_type): %>
-          <img src="<%= App.Config.get('api_path') %>/ticket_attachment/<%= @article.ticket_id %>/<%= @article.id %>/<%= attachment.id %>?view=preview">
+          <img src="<%= App.Config.get('api_path') %>/ticket_attachment/<%= data.article.ticket_id %>/<%= data.article.id %>/<%= data.attachment.id %>?view=preview">
         <% else: %>
           <%- @Icon( @ContentTypeIcon(content_type) ) %>
         <% end %>
@@ -14,8 +13,8 @@
         <%- @Icon('file-unknown') %>
       <% end %>
       </div>
-      <span class="attachment-name u-highlight"><%= attachment.filename %></span>
-      <div class="attachment-size"><%- @humanFileSize(attachment.size) %></div>
+      <span class="attachment-name u-highlight"><%= data.attachment.filename %></span>
+      <div class="attachment-size"><%- @humanTime(data.article.created_at) %> (<%- @humanFileSize(data.attachment.size) %>)</div>
     </a>
   <% end %>
 </div>
diff --git a/app/models/store.rb b/app/models/store.rb
index c9f5cef56..0a956ec56 100644
--- a/app/models/store.rb
+++ b/app/models/store.rb
@@ -216,7 +216,7 @@ returns
   end
 
   def attributes_for_display
-    slice :id, :filename, :size, :preferences
+    slice :id, :store_file_id, :filename, :size, :preferences
   end
 
   RESIZABLE_MIME_REGEXP = %r{image/(jpeg|jpg|png)}i.freeze
diff --git a/spec/system/ticket/zoom_spec.rb b/spec/system/ticket/zoom_spec.rb
index bd5bb44bb..59ae0cff4 100644
--- a/spec/system/ticket/zoom_spec.rb
+++ b/spec/system/ticket/zoom_spec.rb
@@ -2542,4 +2542,52 @@ RSpec.describe 'Ticket zoom', type: :system do
       expect(page).to have_text('SOLUTION TIME')
     end
   end
+
+  context 'Make sidebar attachments unique #3930', authenticated_as: :authenticate do
+    let(:ticket) { create(:ticket, group: Group.find_by(name: 'Users')) }
+    let(:article1)         { create(:ticket_article, ticket: ticket) }
+    let(:article2)         { create(:ticket_article, ticket: ticket) }
+
+    def attachment_add(article, filename)
+      Store.add(
+        object:        'Ticket::Article',
+        o_id:          article.id,
+        data:          "content #{filename}",
+        filename:      filename,
+        preferences:   {
+          'Content-Type' => 'text/plain',
+        },
+        created_by_id: 1,
+      )
+    end
+
+    def authenticate
+      attachment_add(article1, 'some_file.txt')
+      attachment_add(article2, 'some_file.txt')
+      attachment_add(article2, 'some_file2.txt')
+      Setting.set('ui_ticket_zoom_sidebar_article_attachments', true)
+
+      true
+    end
+
+    before do
+      visit "#ticket/zoom/#{ticket.id}"
+      page.find(".tabsSidebar-tabs .tabsSidebar-tab[data-tab='attachment']").click
+    end
+
+    it 'does show the attachment once' do
+      expect(page).to have_selector('.sidebar-content .attachment.attachment--preview', count: 2)
+      expect(page).to have_selector('.sidebar-content', text: 'some_file.txt')
+      expect(page).to have_selector('.sidebar-content', text: 'some_file2.txt')
+    end
+
+    it 'does show up new attachments' do
+      page.find('.js-textarea').send_keys('new article with attachment')
+      page.find('input#fileUpload_1', visible: :all).set(Rails.root.join('test/data/mail/mail001.box'))
+      expect(page).to have_text('mail001.box')
+      wait.until { Taskbar.find_by(key: "Ticket-#{ticket.id}").attributes_with_association_ids['attachments'].present? }
+      click '.js-submit'
+      expect(page).to have_selector('.sidebar-content', text: 'mail001.box')
+    end
+  end
 end