diff --git a/packages/@vuepress/theme-default/components/Page.vue b/packages/@vuepress/theme-default/components/Page.vue
index d086c0b8ba..c0d622a3ac 100644
--- a/packages/@vuepress/theme-default/components/Page.vue
+++ b/packages/@vuepress/theme-default/components/Page.vue
@@ -177,13 +177,7 @@ function resolveNext (page, items) {
 
 function find (page, items, offset) {
   const res = []
-  items.forEach(item => {
-    if (item.type === 'group') {
-      res.push(...item.children || [])
-    } else {
-      res.push(item)
-    }
-  })
+  flatternItems(items, res)
   for (let i = 0; i < res.length; i++) {
     const cur = res[i]
     if (cur.type === 'page' && cur.path === decodeURIComponent(page.path)) {
@@ -191,6 +185,17 @@ function find (page, items, offset) {
     }
   }
 }
+
+function flatternItems (items, res) {
+  for (let i = 0, l = items.length; i < l; i++) {
+    if (items[i].type === 'group') {
+      flatternItems(items[i].children, res)
+    } else {
+      res.push(items[i])
+    }
+  }
+}
+
 </script>
 
 <style lang="stylus">
diff --git a/packages/@vuepress/theme-default/components/Sidebar.vue b/packages/@vuepress/theme-default/components/Sidebar.vue
index 472c667b04..32a9fcf993 100644
--- a/packages/@vuepress/theme-default/components/Sidebar.vue
+++ b/packages/@vuepress/theme-default/components/Sidebar.vue
@@ -2,79 +2,21 @@
   <aside class="sidebar">
     <NavLinks/>
     <slot name="top"/>
-    <ul class="sidebar-links" v-if="items.length">
-      <li v-for="(item, i) in items" :key="i">
-        <SidebarGroup
-          v-if="item.type === 'group'"
-          :item="item"
-          :first="i === 0"
-          :open="i === openGroupIndex"
-          :collapsable="item.collapsable || item.collapsible"
-          @toggle="toggleGroup(i)"
-        />
-        <SidebarLink v-else :item="item"/>
-      </li>
-    </ul>
+    <SidebarLinks class="sidebar-links" :items="items"/>
     <slot name="bottom"/>
   </aside>
 </template>
 
 <script>
-import SidebarGroup from './SidebarGroup.vue'
-import SidebarLink from './SidebarLink.vue'
+import SidebarLinks from './SidebarLinks.vue'
 import NavLinks from './NavLinks.vue'
-import { isActive } from '../util'
 
 export default {
-  components: { SidebarGroup, SidebarLink, NavLinks },
+  name: 'Sidebar',
 
-  props: ['items'],
+  components: { SidebarLinks, NavLinks },
 
-  data () {
-    return {
-      openGroupIndex: 0
-    }
-  },
-
-  created () {
-    this.refreshIndex()
-  },
-
-  watch: {
-    '$route' () {
-      this.refreshIndex()
-    }
-  },
-
-  methods: {
-    refreshIndex () {
-      const index = resolveOpenGroupIndex(
-        this.$route,
-        this.items
-      )
-      if (index > -1) {
-        this.openGroupIndex = index
-      }
-    },
-
-    toggleGroup (index) {
-      this.openGroupIndex = index === this.openGroupIndex ? -1 : index
-    },
-
-    isActive (page) {
-      return isActive(this.$route, page.regularPath)
-    }
-  }
-}
-
-function resolveOpenGroupIndex (route, items) {
-  for (let i = 0; i < items.length; i++) {
-    const item = items[i]
-    if (item.type === 'group' && item.children.some(c => isActive(route, c.path))) {
-      return i
-    }
-  }
-  return -1
+  props: ['items']
 }
 </script>
 
diff --git a/packages/@vuepress/theme-default/components/SidebarGroup.vue b/packages/@vuepress/theme-default/components/SidebarGroup.vue
index 9c0ffc001f..af2e9e16f4 100644
--- a/packages/@vuepress/theme-default/components/SidebarGroup.vue
+++ b/packages/@vuepress/theme-default/components/SidebarGroup.vue
@@ -1,7 +1,7 @@
 <template>
   <section
     class="sidebar-group"
-    :class="{ first, collapsable }"
+    :class="{ collapsable }"
   >
     <router-link
       class="sidebar-heading clickable"
@@ -36,28 +36,28 @@
     </p>
 
     <DropdownTransition>
-      <ul
-        ref="items"
+      <SidebarLinks
         class="sidebar-group-items"
+        :items="item.children"
         v-if="open || !collapsable"
-      >
-        <li v-for="child in item.children">
-          <SidebarLink :item="child"/>
-        </li>
-      </ul>
+        :sidebarDepth="item.sidebarDepth"
+      />
     </DropdownTransition>
   </section>
 </template>
 
 <script>
 import { isActive } from '../util'
-import SidebarLink from './SidebarLink.vue'
 import DropdownTransition from './DropdownTransition.vue'
 
 export default {
   name: 'SidebarGroup',
-  props: ['item', 'first', 'open', 'collapsable'],
-  components: { SidebarLink, DropdownTransition },
+  props: ['item', 'open', 'collapsable'],
+  components: { DropdownTransition },
+  // ref: https://vuejs.org/v2/guide/components-edge-cases.html#Circular-References-Between-Components
+  beforeCreate () {
+    this.$options.components.SidebarLinks = require('./SidebarLinks.vue').default
+  },
   methods: { isActive }
 }
 </script>
@@ -78,7 +78,7 @@ export default {
   font-size 1.1em
   font-weight bold
   // text-transform uppercase
-  padding 0.35rem 1.5rem
+  padding 0.35rem 1.5rem 0.35rem 1.25rem
   width 100%
   box-sizing border-box
   margin 0
diff --git a/packages/@vuepress/theme-default/components/SidebarLink.vue b/packages/@vuepress/theme-default/components/SidebarLink.vue
index 0a38894306..6fb03149b5 100644
--- a/packages/@vuepress/theme-default/components/SidebarLink.vue
+++ b/packages/@vuepress/theme-default/components/SidebarLink.vue
@@ -4,7 +4,7 @@ import { isActive, hashRE, groupHeaders } from '../util'
 export default {
   functional: true,
 
-  props: ['item'],
+  props: ['item', 'sidebarDepth'],
 
   render (h,
     {
@@ -16,7 +16,8 @@ export default {
         $themeLocaleConfig
       },
       props: {
-        item
+        item,
+        sidebarDepth
       }
     }) {
     // use custom active class matching logic
@@ -28,9 +29,16 @@ export default {
       ? selfActive || item.children.some(c => isActive($route, item.basePath + '#' + c.slug))
       : selfActive
     const link = renderLink(h, item.path, item.title || item.path, active)
-    const configDepth = $page.frontmatter.sidebarDepth != null
-      ? $page.frontmatter.sidebarDepth
-      : ($themeLocaleConfig.sidebarDepth || $themeConfig.sidebarDepth)
+
+    let configDepth
+    if ($page.frontmatter.sidebarDepth != null) {
+      configDepth = $page.frontmatter.sidebarDepth
+    } else if (sidebarDepth != null) {
+      configDepth = sidebarDepth
+    } else {
+      configDepth = $themeLocaleConfig.sidebarDepth || $themeConfig.sidebarDepth
+    }
+
     const maxDepth = configDepth == null ? 1 : configDepth
 
     const displayAllHeaders = !!$themeLocaleConfig.displayAllHeaders
diff --git a/packages/@vuepress/theme-default/components/SidebarLinks.vue b/packages/@vuepress/theme-default/components/SidebarLinks.vue
new file mode 100644
index 0000000000..2925cee50a
--- /dev/null
+++ b/packages/@vuepress/theme-default/components/SidebarLinks.vue
@@ -0,0 +1,79 @@
+<template>
+  <ul v-if="items.length">
+    <li v-for="(item, i) in items" :key="i">
+      <SidebarGroup
+        v-if="item.type === 'group'"
+        :item="item"
+        :first="i === 0"
+        :open="i === openGroupIndex"
+        :collapsable="item.collapsable || item.collapsible"
+        @toggle="toggleGroup(i)"
+      />
+      <SidebarLink
+        v-else
+        :sidebarDepth="sidebarDepth"
+        :item="item"
+      />
+    </li>
+  </ul>
+</template>
+
+<script>
+import SidebarGroup from './SidebarGroup.vue'
+import SidebarLink from './SidebarLink.vue'
+import { isActive } from '../util'
+
+export default {
+  name: 'SidebarLinks',
+
+  components: { SidebarGroup, SidebarLink },
+
+  props: ['items', 'sidebarDepth'],
+
+  data () {
+    return {
+      openGroupIndex: 0
+    }
+  },
+
+  created () {
+    this.refreshIndex()
+  },
+
+  watch: {
+    '$route' () {
+      this.refreshIndex()
+    }
+  },
+
+  methods: {
+    refreshIndex () {
+      const index = resolveOpenGroupIndex(
+        this.$route,
+        this.items
+      )
+      if (index > -1) {
+        this.openGroupIndex = index
+      }
+    },
+
+    toggleGroup (index) {
+      this.openGroupIndex = index === this.openGroupIndex ? -1 : index
+    },
+
+    isActive (page) {
+      return isActive(this.$route, page.regularPath)
+    }
+  }
+}
+
+function resolveOpenGroupIndex (route, items) {
+  for (let i = 0; i < items.length; i++) {
+    const item = items[i]
+    if (item.type === 'group' && item.children.some(c => c.type === 'page' && isActive(route, c.path))) {
+      return i
+    }
+  }
+  return -1
+}
+</script>
diff --git a/packages/@vuepress/theme-default/util/index.js b/packages/@vuepress/theme-default/util/index.js
index 8fccc69002..1794b1f226 100644
--- a/packages/@vuepress/theme-default/util/index.js
+++ b/packages/@vuepress/theme-default/util/index.js
@@ -208,7 +208,7 @@ function ensureEndingSlash (path) {
     : path + '/'
 }
 
-function resolveItem (item, pages, base, isNested) {
+function resolveItem (item, pages, base, groupDepth = 1) {
   if (typeof item === 'string') {
     return resolvePage(pages, item, base)
   } else if (Array.isArray(item)) {
@@ -216,10 +216,9 @@ function resolveItem (item, pages, base, isNested) {
       title: item[1]
     })
   } else {
-    if (isNested) {
+    if (groupDepth > 3) {
       console.error(
-        '[vuepress] Nested sidebar groups are not supported. ' +
-        'Consider using navbar + categories instead.'
+        '[vuepress] detected a too deep nested sidebar group.'
       )
     }
     const children = item.children || []
@@ -227,7 +226,8 @@ function resolveItem (item, pages, base, isNested) {
       type: 'group',
       path: item.path,
       title: item.title,
-      children: children.map(child => resolveItem(child, pages, base, true)),
+      sidebarDepth: item.sidebarDepth,
+      children: children.map(child => resolveItem(child, pages, base, groupDepth + 1)),
       collapsable: item.collapsable !== false
     }
   }