diff --git a/openwisp_network_topology/static/netjsongraph/js/visualize.js b/openwisp_network_topology/static/netjsongraph/js/visualize.js
index 31860110..981554f4 100644
--- a/openwisp_network_topology/static/netjsongraph/js/visualize.js
+++ b/openwisp_network_topology/static/netjsongraph/js/visualize.js
@@ -20,10 +20,14 @@ django.jQuery(function ($) {
             body.css('overflow', 'hidden');
             inner.css('overflow', 'hidden');
 
-            const closeBtn = document.createElement('button');
-            closeBtn.setAttribute('class', 'closeBtn');
-            closeBtn.innerHTML = '×';
-            overlay.get(0).appendChild(closeBtn);
+            // Check if close button already exists
+            const closeBtn = document.querySelector('.closeBtn');
+            if (!closeBtn) {
+                const newcloseBtn = document.createElement('button');
+                newcloseBtn.setAttribute('class', 'closeBtn');
+                newcloseBtn.innerHTML = '×';
+                overlay.get(0).appendChild(newcloseBtn);
+            }
 
             window.graph = window.loadNetJsonGraph('.djnjg-overlay .inner');
 
diff --git a/openwisp_network_topology/tests/test_selenium.py b/openwisp_network_topology/tests/test_selenium.py
index 1fab8de4..5838627e 100644
--- a/openwisp_network_topology/tests/test_selenium.py
+++ b/openwisp_network_topology/tests/test_selenium.py
@@ -2,6 +2,7 @@
 from django.contrib.staticfiles.testing import StaticLiveServerTestCase
 from django.urls import reverse
 from selenium import webdriver
+from selenium.common.exceptions import ElementClickInterceptedException
 from selenium.webdriver.common.by import By
 from selenium.webdriver.common.desired_capabilities import DesiredCapabilities
 from selenium.webdriver.support import expected_conditions as EC
@@ -151,3 +152,20 @@ def test_topology_non_admin_view_graph_visualizer(self):
         )
         topology_graph_element.click()
         self._assert_topology_graph()
+
+    def test_topology_admin_visualizer_multiple_close_btn_append(self):
+        path = reverse(f'{self.prefix}_topology_change', args=[self.topology.pk])
+        self.login(username=self.admin_username, password=self.admin_password)
+        self.open(path)
+        self.web_driver.find_element(By.CSS_SELECTOR, 'input.visualizelink').click()
+        self._assert_topology_graph()
+        self.web_driver.find_element(By.CLASS_NAME, 'closeBtn').click()
+        # Now try to open visualizer
+        # again and make sure only single
+        # 'closeBtn' element is present in the DOM
+        self.web_driver.find_element(By.CSS_SELECTOR, 'input.visualizelink').click()
+        self._assert_topology_graph()
+        try:
+            self.web_driver.find_element(By.CLASS_NAME, 'closeBtn').click()
+        except ElementClickInterceptedException:
+            self.fail('Multiple "closeBtn" are present in the visualizer DOM')