diff --git a/src/resources/projects/website/templates/sidebar.ejs b/src/resources/projects/website/templates/sidebar.ejs
index 6b410b5230..2679b2ce7c 100644
--- a/src/resources/projects/website/templates/sidebar.ejs
+++ b/src/resources/projects/website/templates/sidebar.ejs
@@ -19,11 +19,13 @@
     // may be displayed in different locations, so this will determine where to display the tools
     // "logo", "title", "search", "fallthrough"
 
+    let hasLogo = sidebar.logo.light || sidebar.logo.dark;
+
     let toolsLocation;
     // Under the title if that will be displayed
     if (sidebar.title && !navbar) {
       toolsLocation = "title";
-    } else if (sidebar.logo) {
+    } else if (sidebar.logo.light || sidebar.logo.dark) {
       toolsLocation = "logo";
     } else if (sidebar.search && sidebar.search !== "overlay") {
       toolsLocation = "search";
@@ -32,9 +34,9 @@
     }
   %>
     
-  <% if (sidebar.logo || (sidebar.title && !navbar)) { %>
-    <div class="pt-lg-2 mt-2 <%= alignCss %> sidebar-header<%= sidebar.logo && sidebar.title ? ' sidebar-header-stacked' : '' %>">
-    <% if (sidebar.logo) { %>
+  <% if (hasLogo || (sidebar.title && !navbar)) { %>
+    <div class="pt-lg-2 mt-2 <%= alignCss %> sidebar-header<%= hasLogo && sidebar.title ? ' sidebar-header-stacked' : '' %>">
+    <% if (hasLogo) { %>
       <a href="<%- sidebar['logo-href'] || '/index.html' %>" class="sidebar-logo-link">
       <% if (sidebar.logo.light) { %>
       <img src="<%- sidebar.logo.light.path %>" alt="<%- sidebar.logo.light.alt || '' %>" class="sidebar-logo light-content py-0 d-lg-inline d-none"/>
diff --git a/tests/docs/smoke-all/website-sidebar/issue-13506-no-logo/.gitignore b/tests/docs/smoke-all/website-sidebar/issue-13506-no-logo/.gitignore
new file mode 100644
index 0000000000..ad293093b0
--- /dev/null
+++ b/tests/docs/smoke-all/website-sidebar/issue-13506-no-logo/.gitignore
@@ -0,0 +1,2 @@
+/.quarto/
+**/*.quarto_ipynb
diff --git a/tests/docs/smoke-all/website-sidebar/issue-13506-no-logo/_quarto.yml b/tests/docs/smoke-all/website-sidebar/issue-13506-no-logo/_quarto.yml
new file mode 100644
index 0000000000..f4f5aa2909
--- /dev/null
+++ b/tests/docs/smoke-all/website-sidebar/issue-13506-no-logo/_quarto.yml
@@ -0,0 +1,22 @@
+project:
+  type: website
+
+website:
+  title: "Issue 13506 - No Logo"
+  navbar:
+    left:
+      - text: "Section A"
+        href: index.qmd
+      - text: "Section B"
+        href: page2.qmd
+  sidebar:
+    - title: "Section A"
+      contents:
+        - index.qmd
+    - title: "Section B"
+      contents:
+        - page2.qmd
+
+format:
+  html:
+    theme: cosmo
diff --git a/tests/docs/smoke-all/website-sidebar/issue-13506-no-logo/index.qmd b/tests/docs/smoke-all/website-sidebar/issue-13506-no-logo/index.qmd
new file mode 100644
index 0000000000..c1ec37b54a
--- /dev/null
+++ b/tests/docs/smoke-all/website-sidebar/issue-13506-no-logo/index.qmd
@@ -0,0 +1,24 @@
+---
+title: "Section A"
+_quarto:
+  tests:
+    html:
+      ensureHtmlElements:
+        -
+          - 'nav.navbar a.nav-link[href$="index.html"].active'
+          - 'nav.navbar a.nav-link[href$="page2.html"]:not(.active)'
+        -
+          - 'a.sidebar-logo-link'
+---
+
+## Section A
+
+This is Section A. When NO logo is configured in the sidebar, the navbar active
+state should work correctly. The "Section A" navbar item should be active on this page.
+
+The bug (issue #13506): After PR #12996, `sidebar.logo` was normalized to
+`{light: undefined, dark: undefined}`, making `if(sidebar.logo)` always true.
+This created empty `<a class="sidebar-logo-link">` elements that interfered with
+the navbar active state detection logic.
+
+See also: [Section B](page2.qmd)
diff --git a/tests/docs/smoke-all/website-sidebar/issue-13506-no-logo/page2.qmd b/tests/docs/smoke-all/website-sidebar/issue-13506-no-logo/page2.qmd
new file mode 100644
index 0000000000..ed4781e222
--- /dev/null
+++ b/tests/docs/smoke-all/website-sidebar/issue-13506-no-logo/page2.qmd
@@ -0,0 +1,20 @@
+---
+title: "Section B"
+_quarto:
+  tests:
+    html:
+      ensureHtmlElements:
+        -
+          - 'nav.navbar a.nav-link[href$="page2.html"].active'
+          - 'nav.navbar a.nav-link[href$="index.html"]:not(.active)'
+        -
+          - 'a.sidebar-logo-link'
+---
+
+## Section B
+
+This is Section B. The "Section B" navbar item should be active on this page,
+demonstrating that the navbar active state detection works correctly without
+empty logo links interfering.
+
+See also: [Section A](index.qmd)