diff --git a/index.js b/index.js
index 7022b73fe..934275ef3 100644
--- a/index.js
+++ b/index.js
@@ -193,11 +193,24 @@ Command.prototype.command = function(nameAndArgs, actionOptsOrExecDesc, execOpts
   this.commands.push(cmd);
   cmd.parseExpectedArgs(args);
   cmd.parent = this;
+  if (!desc) cmd._addCommandListener(); // Add listener to handle nested subcommand
 
   if (desc) return this;
   return cmd;
 };
 
+/**
+ * @api public
+ */
+Command.prototype.addCommand = function(cmd) {
+  if (!cmd._name) throw Error('addCommand name is not specified for command');
+
+  this.commands.push(cmd);
+  cmd.parent = this;
+  cmd._addCommandListener();
+  return this;
+};
+
 /**
  * Define argument syntax for the top-level command.
  *
@@ -301,6 +314,67 @@ Command.prototype._exit = function(exitCode, code, message) {
   process.exit(exitCode);
 };
 
+/**
+ * @api private
+ */
+
+Command.prototype._addCommandListener = function() {
+  var self = this;
+  var listener = function(args, unknown) {
+    // Parse any so-far unknown options
+    args = args || [];
+    unknown = unknown || [];
+
+    var parsed = self.parseOptions(unknown);
+
+    // Leftover arguments need to be pushed back. Fixes issue #56
+    if (parsed.args.length) args = parsed.args.concat(args);
+
+    if (args.length && self.listenerCount(`command:${args[0]}`)) {
+      self.parseArgs(args, parsed.unknown);
+    } else {
+      // Output help if necessary
+      outputHelpIfNecessary(self, parsed.unknown);
+      self._checkForMissingMandatoryOptions();
+
+      // If there are still any unknown options, then we simply die.
+      if (parsed.unknown.length > 0) {
+        self.unknownOption(parsed.unknown[0]);
+      }
+
+      self._args.forEach(function(arg, i) {
+        if (arg.required && args[i] == null) {
+          self.missingArgument(arg.name);
+        } else if (arg.variadic) {
+          if (i !== self._args.length - 1) {
+            self.variadicArgNotLast(arg.name);
+          }
+
+          args[i] = args.splice(i);
+        }
+      });
+
+      self.emit('action', args);
+    }
+  };
+
+  // Add listener to parent, or program.
+  let eventEmitter = this.parent;
+  let eventName = `command:${this._name}`;
+  if (!eventEmitter) {
+    eventEmitter = this; // program
+    eventName = 'program-command';
+  }
+  // Avoid adding listener twice (currently adding on demand from multiple places).
+  if (eventEmitter.listenerCount(eventName) === 0) {
+    eventEmitter.on(eventName, listener);
+  }
+  const aliasEventName = `command:${this._alias}`;
+  if (this._alias && eventEmitter.listenerCount(aliasEventName) === 0) {
+    eventEmitter.on(aliasEventName, listener);
+  }
+};
+
 /**
  * Register callback `fn` for the command.
  *
@@ -320,39 +394,9 @@ Command.prototype._exit = function(exitCode, code, message) {
 
 Command.prototype.action = function(fn) {
   var self = this;
-  var listener = function(args, unknown) {
-    // Parse any so-far unknown options
-    args = args || [];
-    unknown = unknown || [];
-
-    var parsed = self.parseOptions(unknown);
-
-    // Output help if necessary
-    outputHelpIfNecessary(self, parsed.unknown);
-    self._checkForMissingMandatoryOptions();
-
-    // If there are still any unknown options, then we simply
-    // die, unless someone asked for help, in which case we give it
-    // to them, and then we die.
-    if (parsed.unknown.length > 0) {
-      self.unknownOption(parsed.unknown[0]);
-    }
-
-    // Leftover arguments need to be pushed back. Fixes issue #56
-    if (parsed.args.length) args = parsed.args.concat(args);
-
-    self._args.forEach(function(arg, i) {
-      if (arg.required && args[i] == null) {
-        self.missingArgument(arg.name);
-      } else if (arg.variadic) {
-        if (i !== self._args.length - 1) {
-          self.variadicArgNotLast(arg.name);
-        }
-
-        args[i] = args.splice(i);
-      }
-    });
+  this._addCommandListener();
 
+  var listener = function(args) {
     // The .action callback takes an extra parameter which is the command itself.
     var expectedArgsCount = self._args.length;
     var actionArgs = args.slice(0, expectedArgsCount);
@@ -368,14 +412,10 @@ Command.prototype.action = function(fn) {
 
     fn.apply(self, actionArgs);
   };
-  var parent = this.parent || this;
-  if (parent === this) {
-    parent.on('program-command', listener);
-  } else {
-    parent.on('command:' + this._name, listener);
-  }
 
-  if (this._alias) parent.on('command:' + this._alias, listener);
+  this.on('action', listener);
+  if (this._alias) this.on('action', listener);
+
   return this;
 };
 
@@ -874,8 +914,10 @@ Command.prototype.parseArgs = function(args, unknown) {
     if (this.listeners('command:' + name).length) {
       this.emit('command:' + args.shift(), args, unknown);
     } else {
-      this.emit('program-command', args, unknown);
       this.emit('command:*', args, unknown);
+      if (!this.parent) {
+        this.emit('program-command', args, unknown);
+      }
     }
   } else {
     outputHelpIfNecessary(this, unknown);
@@ -885,7 +927,7 @@ Command.prototype.parseArgs = function(args, unknown) {
       this.unknownOption(unknown[0]);
     }
     // Call the program action handler, unless it has a (missing) required parameter and signature does not match.
-    if (this._args.filter(function(a) { return a.required; }).length === 0) {
+    if (!this.parent && this._args.filter(function(a) { return a.required; }).length === 0) {
       this.emit('program-command');
     }
   }