--- a/browser/devtools/webconsole/test/browser.ini
+++ b/browser/devtools/webconsole/test/browser.ini
@@ -216,16 +216,17 @@ support-files =
 [browser_webconsole_chrome.js]
 [browser_webconsole_closure_inspection.js]
 [browser_webconsole_completion.js]
 [browser_webconsole_console_extras.js]
 [browser_webconsole_console_logging_api.js]
 [browser_webconsole_execution_scope.js]
 [browser_webconsole_for_of.js]
 [browser_webconsole_history.js]
+[browser_webconsole_input_field_focus_on_panel_select.js]
 [browser_webconsole_js_input_expansion.js]
 [browser_webconsole_jsterm.js]
 [browser_webconsole_live_filtering_of_message_types.js]
 [browser_webconsole_live_filtering_on_search_strings.js]
 [browser_webconsole_message_node_id.js]
 [browser_webconsole_netlogging.js]
 [browser_webconsole_network_panel.js]
 [browser_webconsole_notifications.js]

new file mode 100644
--- /dev/null
+++ b/browser/devtools/webconsole/test/browser_webconsole_input_field_focus_on_panel_select.js
@@ -0,0 +1,46 @@
+/* Any copyright is dedicated to the Public Domain
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+// Test that the JS input field is focused when the user switches back to the
+// web console from other tools, see bug 891581.
+
+const TEST_URI = "data:text/html;charset=utf8,<p>hello";
+
+function test()
+{
+  addTab(TEST_URI);
+  browser.addEventListener("load", function onLoad() {
+    browser.removeEventListener("load", onLoad, true);
+    openConsole(null, consoleOpened);
+  }, true);
+}
+
+function consoleOpened(hud)
+{
+  is(hud.jsterm.inputNode.hasAttribute("focused"), true,
+     "inputNode should be focused");
+
+  hud.ui.filterBox.focus();
+
+  is(hud.ui.filterBox.hasAttribute("focused"), true,
+     "filterBox should be focused");
+
+  is(hud.jsterm.inputNode.hasAttribute("focused"), false,
+     "inputNode shouldn't be focused");
+
+  openDebugger().then(debuggerOpened);
+}
+
+function debuggerOpened()
+{
+  openConsole(null, consoleReopened);
+}
+
+function consoleReopened(hud)
+{
+  is(hud.jsterm.inputNode.hasAttribute("focused"), true,
+     "inputNode should be focused");
+
+  finishTest();
+}

--- a/browser/devtools/webconsole/webconsole.js
+++ b/browser/devtools/webconsole/webconsole.js
@@ -26,16 +26,17 @@ loader.lazyGetter(this, "ConsoleOutput",
                   () => require("devtools/webconsole/console-output").ConsoleOutput);
 loader.lazyGetter(this, "Messages",
                   () => require("devtools/webconsole/console-output").Messages);
 loader.lazyImporter(this, "EnvironmentClient", "resource://gre/modules/devtools/dbg-client.jsm");
 loader.lazyImporter(this, "ObjectClient", "resource://gre/modules/devtools/dbg-client.jsm");
 loader.lazyImporter(this, "VariablesView", "resource:///modules/devtools/VariablesView.jsm");
 loader.lazyImporter(this, "VariablesViewController", "resource:///modules/devtools/VariablesViewController.jsm");
 loader.lazyImporter(this, "PluralForm", "resource://gre/modules/PluralForm.jsm");
+loader.lazyImporter(this, "gDevTools", "resource:///modules/devtools/gDevTools.jsm");
 
 const STRINGS_URI = "chrome://browser/locale/devtools/webconsole.properties";
 let l10n = new WebConsoleUtils.l10n(STRINGS_URI);
 
 const XHTML_NS = "http://www.w3.org/1999/xhtml";
 
 const MIXED_CONTENT_LEARN_MORE = "https://developer.mozilla.org/docs/Security/MixedContent";
 
@@ -193,16 +194,17 @@ function WebConsoleFrame(aWebConsoleOwne
   this._outputQueue = [];
   this._pruneCategoriesQueue = {};
   this._networkRequests = {};
   this.filterPrefs = {};
 
   this.output = new ConsoleOutput(this);
 
   this._toggleFilter = this._toggleFilter.bind(this);
+  this._onPanelSelected = this._onPanelSelected.bind(this);
   this._flushMessageQueue = this._flushMessageQueue.bind(this);
 
   this._outputTimer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
   this._outputTimerInitialized = false;
 
   EventEmitter.decorate(this);
 }
 exports.WebConsoleFrame = WebConsoleFrame;
@@ -550,16 +552,31 @@ WebConsoleFrame.prototype = {
     clearButton.addEventListener("command", () => {
       this.owner._onClearButton();
       this.jsterm.clearOutput(true);
     });
 
     this.jsterm = new JSTerm(this);
     this.jsterm.init();
     this.jsterm.inputNode.focus();
+
+    let toolbox = gDevTools.getToolbox(this.owner.target);
+    if (toolbox) {
+      toolbox.on("webconsole-selected", this._onPanelSelected);
+    }
+  },
+
+  /**
+   * Sets the focus to JavaScript input field when the web console tab is
+   * selected.
+   * @private
+   */
+  _onPanelSelected: function WCF__onPanelSelected()
+  {
+    this.jsterm.inputNode.focus();
   },
 
   /**
    * Initialize the default filter preferences.
    * @private
    */
   _initDefaultFilterPrefs: function WCF__initDefaultFilterPrefs()
   {
@@ -2821,16 +2838,21 @@ WebConsoleFrame.prototype = {
   destroy: function WCF_destroy()
   {
     if (this._destroyer) {
       return this._destroyer.promise;
     }
 
     this._destroyer = promise.defer();
 
+    let toolbox = gDevTools.getToolbox(this.owner.target);
+    if (toolbox) {
+      toolbox.off("webconsole-selected", this._onPanelSelected);
+    }
+
     this._repeatNodes = {};
     this._outputQueue = [];
     this._pruneCategoriesQueue = {};
     this._networkRequests = {};
 
     if (this._outputTimerInitialized) {
       this._outputTimerInitialized = false;
       this._outputTimer.cancel();