diff --git a/app/models/command/filter_by_tag.rb b/app/models/command/filter_by_tag.rb
index 8c6a49e74..f62aca01a 100644
--- a/app/models/command/filter_by_tag.rb
+++ b/app/models/command/filter_by_tag.rb
@@ -1,18 +1,13 @@
 class Command::FilterByTag < Command
-  store_accessor :data, :tag_id, :params
+  include Command::Tags
 
-  validates_presence_of :tag_id
+  store_accessor :data, :params
 
   def title
-    "Filter by tag ##{tag&.title || tag_id} "
+    "Filter by tag ##{tag_title}"
   end
 
   def execute
-    redirect_to cards_path(**params.merge(tag_ids: [ tag_id ]))
+    redirect_to cards_path(**params.merge(tag_ids: [ tag.id ]))
   end
-
-  private
-    def tag
-      Tag.find_by_id(tag_id)
-    end
 end
diff --git a/app/models/command/parser.rb b/app/models/command/parser.rb
index 8fbd5ccc3..ea330420a 100644
--- a/app/models/command/parser.rb
+++ b/app/models/command/parser.rb
@@ -19,14 +19,16 @@ class Command::Parser
       command_name, *command_arguments = string.strip.split(" ")
 
       case command_name
+      when /^#/
+        Command::FilterByTag.new(tag_title: tag_title_from(string), params: filter.as_params)
+      when /^@/
+        Command::GoToUser.new(user_id: assignee_from(command_name)&.id)
       when "/assign", "/assignto"
         Command::Assign.new(assignee_ids: assignees_from(command_arguments).collect(&:id), card_ids: cards.ids)
       when "/close"
         Command::Close.new(card_ids: cards.ids, reason: command_arguments.join(" "))
-      when /^#/
-        Command::FilterByTag.new(tag_id: tag_from(string).id, params: filter.as_params)
-      when /^@/
-        Command::GoToUser.new(user_id: assignee_from(command_name)&.id)
+      when "/tag"
+        Command::Tag.new(tag_title: tag_title_from(command_arguments.join(" ")), card_ids: cards.ids)
       else
         parse_free_string(string)
       end
@@ -46,9 +48,8 @@ class Command::Parser
       User.all.find { |user| user.mentionable_handles.include?(string_without_at) }
     end
 
-    def tag_from(string)
-      title = string.gsub(/^#/, "")
-      Tag.find_or_create_by!(title: title)
+    def tag_title_from(string)
+      string.gsub(/^#/, "")
     end
 
     def parse_free_string(string)
diff --git a/app/models/command/tag.rb b/app/models/command/tag.rb
new file mode 100644
index 000000000..c6596de56
--- /dev/null
+++ b/app/models/command/tag.rb
@@ -0,0 +1,37 @@
+class Command::Tag < Command
+  include Command::Cards, Command::Tags
+
+  store_accessor :data, :tagged_card_ids
+
+  def title
+    "Tag #{cards_description} with ##{tag_title}"
+  end
+
+  def execute
+    tagged_card_ids = []
+
+    transaction do
+      cards.find_each do |card|
+        unless card.tagged_with?(tag)
+          tagged_card_ids << card.id
+          card.toggle_tag_with(tag_title)
+        end
+      end
+
+      update! tagged_card_ids: tagged_card_ids
+    end
+  end
+
+  def undo
+    transaction do
+      tagged_cards.find_each do |card|
+        card.toggle_tag_with(tag_title) if card.tagged_with?(tag)
+      end
+    end
+  end
+
+  private
+    def tagged_cards
+      user.accessible_cards.where(id: tagged_card_ids)
+    end
+end
diff --git a/app/models/command/tags.rb b/app/models/command/tags.rb
new file mode 100644
index 000000000..448c7375c
--- /dev/null
+++ b/app/models/command/tags.rb
@@ -0,0 +1,14 @@
+module Command::Tags
+  extend ActiveSupport::Concern
+
+  included do
+    store_accessor :data, :tag_title
+
+    validates_presence_of :tag_title
+  end
+
+  private
+    def tag
+      Tag.find_or_create_by!(title: tag_title)
+    end
+end
diff --git a/test/models/command/filter_by_tag_test.rb b/test/models/command/filter_by_tag_test.rb
index ef335a1d3..53be19ca9 100644
--- a/test/models/command/filter_by_tag_test.rb
+++ b/test/models/command/filter_by_tag_test.rb
@@ -7,7 +7,7 @@ class Command::FilterByCardTest < ActionDispatch::IntegrationTest
     @tag = tags(:web)
   end
 
-  test "redirects to the cards index filtering by cards" do
+  test "redirect to the cards index filtering by cards" do
     result = execute_command "##{@tag.title}"
 
     assert_equal cards_path(indexed_by: "newest", tag_ids: [ @tag.id ]), result.url
diff --git a/test/models/command/tag_test.rb b/test/models/command/tag_test.rb
new file mode 100644
index 000000000..7c3486b34
--- /dev/null
+++ b/test/models/command/tag_test.rb
@@ -0,0 +1,47 @@
+require "test_helper"
+
+class Command::TagTest < ActionDispatch::IntegrationTest
+  include CommandTestHelper
+
+  setup do
+    Current.session = sessions(:david)
+    @card = cards(:text)
+    @tag = tags(:web)
+  end
+
+  test "tag card on perma with existing tag" do
+    assert_changes -> { @card.tagged_with?(@tag) }, from: false, to: true do
+      execute_command "/tag #{@tag.title}", context_url: collection_card_url(@card.collection, @card)
+    end
+  end
+
+  test "tag card on perma with new card" do
+    assert_difference -> { @card.tags.count }, +1 do
+      execute_command "/tag some-new-tag", context_url: collection_card_url(@card.collection, @card)
+    end
+
+    assert_equal "some-new-tag", @card.tags.last.title
+  end
+
+  test "tag several cards on cards' index page" do
+    cards = cards(:logo, :text, :layout)
+    cards.each { it.taggings.destroy_all }
+
+    execute_command "/tag #{@tag.title}", context_url: collection_cards_url(@card.collection)
+
+    cards.each { assert it.reload.tagged_with?(@tag) }
+  end
+
+  test "undo tagged cards" do
+    cards = cards(:logo, :text, :layout)
+    cards.each { it.taggings.destroy_all }
+
+    command = parse_command "/tag #{@tag.title}", context_url: collection_cards_url(@card.collection)
+    command.execute
+
+    cards.each { assert it.reload.tagged_with?(@tag) }
+
+    command.undo
+    cards.each { assert_not it.reload.tagged_with?(@tag) }
+  end
+end