diff --git a/features/cli/debug.feature b/features/cli/debug.feature
new file mode 100644
index 0000000..19f1497
--- /dev/null
+++ b/features/cli/debug.feature
@@ -0,0 +1,5 @@
+Feature: debug CLI option
+
+  Scenario: raises the logger level to DEBUG
+    When I run uhwm with option -d
+    Then the current output must match /log.+debug.+level/i
diff --git a/features/steps/output_steps.rb b/features/steps/output_steps.rb
index 558dd10..14f53a2 100644
--- a/features/steps/output_steps.rb
+++ b/features/steps/output_steps.rb
@@ -22,6 +22,7 @@ Usage: uhwm [options]
 options:
     -h, --help                       print this message
     -v, --version                    enable verbose mode
+    -d, --debug                      enable debug mode
   eoh
 end
 
diff --git a/lib/uh/wm/cli.rb b/lib/uh/wm/cli.rb
index 4330cc1..6bb70bf 100644
--- a/lib/uh/wm/cli.rb
+++ b/lib/uh/wm/cli.rb
@@ -53,6 +53,11 @@ module Uh
             @env.verbose = true
             @env.log_logger_level
           end
+
+          opts.on '-d', '--debug', 'enable debug mode' do
+            @env.debug = true
+            @env.log_logger_level
+          end
         end
       end
     end
diff --git a/lib/uh/wm/env.rb b/lib/uh/wm/env.rb
index 7a42b29..b750493 100644
--- a/lib/uh/wm/env.rb
+++ b/lib/uh/wm/env.rb
@@ -3,6 +3,7 @@ module Uh
     class Env
       LOGGER_LEVEL          = Logger::WARN
       LOGGER_LEVEL_VERBOSE  = Logger::INFO
+      LOGGER_LEVEL_DEBUG    = Logger::DEBUG
       LOGGER_LEVEL_STRINGS = %w[DEBUG INFO WARN ERROR FATAL UNKNOWN]
 
       extend Forwardable
@@ -10,7 +11,7 @@ module Uh
       def_delegator :@output, :print
 
       attr_reader   :output
-      attr_accessor :verbose
+      attr_accessor :verbose, :debug
 
       def initialize output
         @output = output
@@ -20,9 +21,14 @@ module Uh
         !!@verbose
       end
 
+      def debug?
+        !!@debug
+      end
+
       def logger
         @logger ||= Logger.new(@output).tap do |o|
-          o.level = verbose? ? LOGGER_LEVEL_VERBOSE : LOGGER_LEVEL
+          o.level = debug? ? LOGGER_LEVEL_DEBUG :
+            verbose? ? LOGGER_LEVEL_VERBOSE : LOGGER_LEVEL
         end
       end
 
diff --git a/spec/uh/wm/cli_spec.rb b/spec/uh/wm/cli_spec.rb
index d901983..4fd9f7f 100644
--- a/spec/uh/wm/cli_spec.rb
+++ b/spec/uh/wm/cli_spec.rb
@@ -102,6 +102,20 @@ module Uh
           end
         end
 
+        context 'with debug option' do
+          let(:arguments) { %w[-d] }
+
+          it 'sets the env as debug' do
+            cli.parse_arguments!
+            expect(cli.env).to be_debug
+          end
+
+          it 'tells the env to log its logger level' do
+            expect(cli.env).to receive :log_logger_level
+            cli.parse_arguments!
+          end
+        end
+
         context 'with invalid option' do
           let(:arguments) { %w[--unknown-option] }
 
diff --git a/spec/uh/wm/env_spec.rb b/spec/uh/wm/env_spec.rb
index f9f1cfb..4b89b04 100644
--- a/spec/uh/wm/env_spec.rb
+++ b/spec/uh/wm/env_spec.rb
@@ -9,6 +9,10 @@ module Uh
         expect(env).not_to be_verbose
       end
 
+      it 'has debug mode disabled' do
+        expect(env).not_to be_debug
+      end
+
       describe '#verbose?' do
         context 'when verbose mode is disabled' do
           before { env.verbose = false }
@@ -27,6 +31,24 @@ module Uh
         end
       end
 
+      describe '#debug?' do
+        context 'when debug mode is disabled' do
+          before { env.debug = false }
+
+          it 'returns false' do
+            expect(env.debug?).to be false
+          end
+        end
+
+        context 'when debug mode is enabled' do
+          before { env.debug = true }
+
+          it 'returns true' do
+            expect(env.debug?).to be true
+          end
+        end
+      end
+
       describe '#logger' do
         it 'returns a logger' do
           expect(env.logger).to be_a Logger
@@ -39,9 +61,17 @@ module Uh
         context 'when verbose mode is enabled' do
           before { env.verbose = true }
 
-        it 'has logger level info set' do
-          expect(env.logger.level).to be Logger::INFO
+          it 'has logger level info set' do
+            expect(env.logger.level).to be Logger::INFO
+          end
         end
+
+        context 'when debug mode is enabled' do
+          before { env.debug = true }
+
+          it 'has logger level debug set' do
+            expect(env.logger.level).to be Logger::DEBUG
+          end
         end
       end