diff --git a/extensions/tags/js/forum/src/components/TagDiscussionModal.js b/extensions/tags/js/forum/src/components/TagDiscussionModal.js
index 090811a1f..ddd6ddadf 100644
--- a/extensions/tags/js/forum/src/components/TagDiscussionModal.js
+++ b/extensions/tags/js/forum/src/components/TagDiscussionModal.js
@@ -3,6 +3,7 @@ import DiscussionPage from 'flarum/components/DiscussionPage';
 import Button from 'flarum/components/Button';
 import highlight from 'flarum/helpers/highlight';
 import classList from 'flarum/utils/classList';
+import extractText from 'flarum/utils/extractText';
 
 import tagLabel from 'tags/helpers/tagLabel';
 import tagIcon from 'tags/helpers/tagIcon';
@@ -24,6 +25,19 @@ export default class TagDiscussionModal extends Modal {
     } else if (this.props.discussion) {
       this.props.discussion.tags().map(this.addTag.bind(this));
     }
+
+    this.minPrimary = app.forum.attribute('minPrimaryTags');
+    this.maxPrimary = app.forum.attribute('maxPrimaryTags');
+    this.minSecondary = app.forum.attribute('minSecondaryTags');
+    this.maxSecondary = app.forum.attribute('maxSecondaryTags');
+  }
+
+  primaryCount() {
+    return this.selected.filter(tag => tag.isPrimary()).length;
+  }
+
+  secondaryCount() {
+    return this.selected.filter(tag => !tag.isPrimary()).length;
   }
 
   /**
@@ -75,17 +89,46 @@ export default class TagDiscussionModal extends Modal {
       : app.trans('tags.tag_new_discussion_title');
   }
 
+  getInstruction(primaryCount, secondaryCount) {
+    if (primaryCount < this.minPrimary) {
+      return app.trans('tags.choose_primary_tags', {count: this.minPrimary - primaryCount});
+    } else if (secondaryCount < this.minSecondary) {
+      return app.trans('tags.choose_secondary_tags', {count: this.minSecondary - secondaryCount});
+    }
+
+    return '';
+  }
+
   content() {
     let tags = this.tags;
     const filter = this.filter().toLowerCase();
+    const primaryCount = this.primaryCount();
+    const secondaryCount = this.secondaryCount();
 
+    // Filter out all child tags whose parents have not been selected. This
+    // makes it impossible to select a child if its parent hasn't been selected.
+    tags = tags.filter(tag => {
+      const parent = tag.parent();
+      return parent === false || this.selected.indexOf(parent) !== -1;
+    });
+
+    // If the number of selected primary/secondary tags is at the maximum, then
+    // we'll filter out all other tags of that type.
+    if (primaryCount >= app.forum.attribute('maxPrimaryTags')) {
+      tags = tags.filter(tag => !tag.isPrimary() || this.selected.indexOf(tag) !== -1);
+    }
+
+    if (secondaryCount >= app.forum.attribute('maxSecondaryTags')) {
+      tags = tags.filter(tag => tag.isPrimary() || this.selected.indexOf(tag) !== -1);
+    }
+
+    // If the user has entered text in the filter input, then filter by tags
+    // whose name matches what they've entered.
     if (filter) {
       tags = tags.filter(tag => tag.name().substr(0, filter.length).toLowerCase() === filter);
     }
 
-    if (tags.indexOf(this.index) === -1) {
-      this.index = tags[0];
-    }
+    if (tags.indexOf(this.index) === -1) this.index = tags[0];
 
     return [
       <div className="Modal-body">
@@ -103,7 +146,7 @@ export default class TagDiscussionModal extends Modal {
                 )}
               </span>
               <input className="FormControl"
-                placeholder={!this.selected.length ? app.trans('tags.discussion_tags_placeholder') : ''}
+                placeholder={extractText(this.getInstruction(primaryCount, secondaryCount))}
                 value={this.filter()}
                 oninput={m.withAttr('value', this.filter)}
                 onkeydown={this.onkeydown.bind(this)}
@@ -115,7 +158,7 @@ export default class TagDiscussionModal extends Modal {
             {Button.component({
               type: 'submit',
               className: 'Button Button--primary',
-              disabled: !this.selected.length,
+              disabled: primaryCount < this.minPrimary || secondaryCount < this.minSecondary,
               icon: 'check',
               children: app.trans('tags.confirm')
             })}
@@ -125,12 +168,9 @@ export default class TagDiscussionModal extends Modal {
 
       <div className="Modal-footer">
         <ul className="TagDiscussionModal-list SelectTagList">
-          {tags.map(tag => {
-            if (!filter && tag.parent() && this.selected.indexOf(tag.parent()) === -1) {
-              return '';
-            }
-
-            return (
+          {tags
+            .filter(tag => filter || !tag.parent() || this.selected.indexOf(tag.parent()) !== -1)
+            .map(tag => (
               <li data-index={tag.id()}
                 className={classList({
                   pinned: tag.position() !== null,
@@ -154,8 +194,7 @@ export default class TagDiscussionModal extends Modal {
                     </span>
                   ) : ''}
               </li>
-            );
-          })}
+            ))}
         </ul>
       </div>
     ];
diff --git a/extensions/tags/js/lib/models/Tag.js b/extensions/tags/js/lib/models/Tag.js
index 0cfcb74a7..391a4a7bc 100644
--- a/extensions/tags/js/lib/models/Tag.js
+++ b/extensions/tags/js/lib/models/Tag.js
@@ -1,5 +1,6 @@
 import Model from 'flarum/Model';
 import mixin from 'flarum/utils/mixin';
+import computed from 'flarum/utils/computed';
 
 export default class Tag extends mixin(Model, {
   name: Model.attribute('name'),
@@ -21,5 +22,7 @@ export default class Tag extends mixin(Model, {
   lastDiscussion: Model.hasOne('lastDiscussion'),
 
   isRestricted: Model.attribute('isRestricted'),
-  canStartDiscussion: Model.attribute('canStartDiscussion')
+  canStartDiscussion: Model.attribute('canStartDiscussion'),
+
+  isPrimary: computed('position', 'parent', (position, parent) => position !== null && parent === false)
 }) {}
diff --git a/extensions/tags/less/forum/TagDiscussionModal.less b/extensions/tags/less/forum/TagDiscussionModal.less
index e5ba8bd0f..2cdb63cbe 100644
--- a/extensions/tags/less/forum/TagDiscussionModal.less
+++ b/extensions/tags/less/forum/TagDiscussionModal.less
@@ -58,8 +58,12 @@
   cursor: not-allowed;
 }
 .TagsInput-selected {
-  .TagLabel {
+  .TagsInput-tag {
     margin-right: 5px;
+
+    &:last-child {
+      margin-right: 10px;
+    }
   }
 }
 
diff --git a/extensions/tags/locale/en.yml b/extensions/tags/locale/en.yml
index d536396d3..66846de51 100644
--- a/extensions/tags/locale/en.yml
+++ b/extensions/tags/locale/en.yml
@@ -7,7 +7,12 @@ tags:
   tag_new_discussion_title: Choose Tags for Your Discussion
   edit_discussion_tags_title: "Edit Tags for {title}"
   edit_discussion_tags_link: Edit Tags
-  discussion_tags_placeholder: Choose one or more topics
+  choose_primary_tags:
+    one: Choose a primary tag
+    other: "Choose {count} primary tags"
+  choose_secondary_tags:
+    one: Choose 1 more tag
+    other: "Choose {count} more tags"
   confirm: Confirm
   more: More...
   tag_cloud_title: Tags
diff --git a/extensions/tags/src/Listeners/AddApiAttributes.php b/extensions/tags/src/Listeners/AddApiAttributes.php
index 33ddaf64e..8668b50bd 100755
--- a/extensions/tags/src/Listeners/AddApiAttributes.php
+++ b/extensions/tags/src/Listeners/AddApiAttributes.php
@@ -70,6 +70,15 @@ class AddApiAttributes
         if ($event->serializer instanceof DiscussionSerializer) {
             $event->attributes['canTag'] = $event->model->can($event->actor, 'tag');
         }
+
+        if ($event->serializer instanceof ForumSerializer) {
+            $settings = app('Flarum\Core\Settings\SettingsRepository');
+
+            $event->attributes['minPrimaryTags'] = $settings->get('tags.min_primary_tags');
+            $event->attributes['maxPrimaryTags'] = $settings->get('tags.max_primary_tags');
+            $event->attributes['minSecondaryTags'] = $settings->get('tags.min_secondary_tags');
+            $event->attributes['maxSecondaryTags'] = $settings->get('tags.max_secondary_tags');
+        }
     }
 
     public function addRoutes(RegisterApiRoutes $event)
diff --git a/extensions/tags/src/Listeners/AddClientAssets.php b/extensions/tags/src/Listeners/AddClientAssets.php
index 242c28fb4..9d311ad82 100755
--- a/extensions/tags/src/Listeners/AddClientAssets.php
+++ b/extensions/tags/src/Listeners/AddClientAssets.php
@@ -35,7 +35,8 @@ class AddClientAssets
             'tags.tag_new_discussion_title',
             'tags.edit_discussion_tags_title',
             'tags.edit_discussion_tags_link',
-            'tags.discussion_tags_placeholder',
+            'tags.choose_primary_tags',
+            'tags.choose_secondary_tags',
             'tags.confirm',
             'tags.more',
             'tags.tag_cloud_title',
diff --git a/extensions/tags/src/Listeners/PersistData.php b/extensions/tags/src/Listeners/PersistData.php
index 6099b1f19..cacf96b9c 100755
--- a/extensions/tags/src/Listeners/PersistData.php
+++ b/extensions/tags/src/Listeners/PersistData.php
@@ -5,9 +5,18 @@ use Flarum\Tags\Events\DiscussionWasTagged;
 use Flarum\Events\DiscussionWillBeSaved;
 use Flarum\Core\Discussions\Discussion;
 use Flarum\Core\Exceptions\PermissionDeniedException;
+use Flarum\Core\Settings\SettingsRepository;
+use Flarum\Tags\TagCountException;
 
 class PersistData
 {
+    protected $settings;
+
+    public function __construct(SettingsRepository $settings)
+    {
+        $this->settings = $settings;
+    }
+
     public function subscribe($events)
     {
         $events->listen(DiscussionWillBeSaved::class, [$this, 'whenDiscussionWillBeSaved']);
@@ -25,13 +34,25 @@ class PersistData
                 $newTagIds[] = (int) $link['id'];
             }
 
-            $newTags = Tag::whereIn('id', $newTagIds);
+            $newTags = Tag::whereIn('id', $newTagIds)->get();
+            $primaryCount = 0;
+            $secondaryCount = 0;
+
             foreach ($newTags as $tag) {
                 if (! $tag->can($actor, 'startDiscussion')) {
                     throw new PermissionDeniedException;
                 }
+
+                if ($tag->position !== null && $tag->parent_id === null) {
+                    $primaryCount++;
+                } else {
+                    $secondaryCount++;
+                }
             }
 
+            $this->validatePrimaryTagCount($primaryCount);
+            $this->validateSecondaryTagCount($secondaryCount);
+
             $oldTags = [];
 
             if ($discussion->exists) {
@@ -50,4 +71,24 @@ class PersistData
             });
         }
     }
+
+    protected function validatePrimaryTagCount($count)
+    {
+        $min = $this->settings->get('tags.min_primary_tags');
+        $max = $this->settings->get('tags.max_primary_tags');
+
+        if ($count < $min || $count > $max) {
+            throw new TagCountException(['tags' => sprintf('Discussion must have between %d and %d primary tags.', $min, $max)]);
+        }
+    }
+
+    protected function validateSecondaryTagCount($count)
+    {
+        $min = $this->settings->get('tags.min_secondary_tags');
+        $max = $this->settings->get('tags.max_secondary_tags');
+
+        if ($count < $min || $count > $max) {
+            throw new TagCountException(['tags' => sprintf('Discussion must have between %d and %d secondary tags.', $min, $max)]);
+        }
+    }
 }
diff --git a/extensions/tags/src/TagCountException.php b/extensions/tags/src/TagCountException.php
new file mode 100644
index 000000000..b59614d2b
--- /dev/null
+++ b/extensions/tags/src/TagCountException.php
@@ -0,0 +1,7 @@
+<?php namespace Flarum\Tags;
+
+use Flarum\Core\Exceptions\ValidationException;
+
+class TagCountException extends ValidationException
+{
+}