--- a/browser/modules/BrowserUsageTelemetry.jsm
+++ b/browser/modules/BrowserUsageTelemetry.jsm
@@ -131,16 +131,30 @@ const KNOWN_ADDONS = [];
 const SET_USAGE_PREF_BUTTONS = [
   "downloads-button",
   "fxa-toolbar-menu-button",
   "home-button",
   "sidebar-button",
   "library-button",
 ];
 
+// Buttons that, when clicked, increase a counter. The convention
+// is that the preference is named:
+//
+// browser.engagement.<button id>.used-count
+//
+// and doesn't have a default value.
+const SET_USAGECOUNT_PREF_BUTTONS = [
+  "pageAction-panel-copyURL",
+  "pageAction-panel-emailLink",
+  "pageAction-panel-pinTab",
+  "pageAction-panel-screenshots_mozilla_org",
+  "pageAction-panel-shareURL",
+];
+
 function telemetryId(widgetId, obscureAddons = true) {
   // Add-on IDs need to be obscured.
   function addonId(id) {
     if (!obscureAddons) {
       return id;
     }
 
     let pos = KNOWN_ADDONS.indexOf(id);
@@ -823,17 +837,20 @@ let BrowserUsageTelemetry = {
     }
 
     let item = this._getWidgetID(node);
     let source = this._getWidgetContainer(node);
 
     if (item && source) {
       let scalar = `browser.ui.interaction.${source.replace("-", "_")}`;
       Services.telemetry.keyedScalarAdd(scalar, telemetryId(item), 1);
-
+      if (SET_USAGECOUNT_PREF_BUTTONS.includes(item)) {
+        let pref = `browser.engagement.${item}.used-count`;
+        Services.prefs.setIntPref(pref, Services.prefs.getIntPref(pref, 0) + 1);
+      }
       if (SET_USAGE_PREF_BUTTONS.includes(item)) {
         Services.prefs.setBoolPref(`browser.engagement.${item}.has-used`, true);
       }
     }
   },
 
   /**
    * Listens for UI interactions in the window.

--- a/browser/modules/test/browser/browser_UsageTelemetry_usagePrefs.js
+++ b/browser/modules/test/browser/browser_UsageTelemetry_usagePrefs.js
@@ -74,8 +74,69 @@ add_task(async function test_usage_ctrlt
 
   EventUtils.synthesizeKey("VK_TAB", { ctrlKey: true });
 
   Assert.ok(
     Services.prefs.getBoolPref(ctrlTabUsed),
     `${ctrlTabUsed} should now be true after interacting.`
   );
 });
+
+/**
+ * Tests that browser.engagement.pageAction-panel-*.used.count is incremented
+ * when user clicks on certain page action buttons.
+ */
+add_task(async function test_usage_pageAction_buttons() {
+  // Skip the test if proton is enabled, since these buttons are hidden.
+  if (gProton) {
+    return;
+  }
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.screenshots.disabled", false]],
+  });
+
+  const { sinon } = ChromeUtils.import("resource://testing-common/Sinon.jsm");
+  const sandbox = sinon.createSandbox();
+  registerCleanupFunction(sandbox.restore);
+  sandbox.stub(BrowserPageActions, "doCommandForAction").callsFake(() => {});
+
+  await BrowserTestUtils.withNewTab("http://example.com/", async browser => {
+    info("Open the pageAction panel");
+    await promiseOpenPageActionPanel();
+
+    function click(button) {
+      info(`Click on ${button.id}`);
+      EventUtils.synthesizeMouseAtCenter(button, {}, window);
+    }
+
+    let ids = [
+      "pageAction-panel-copyURL",
+      "pageAction-panel-emailLink",
+      "pageAction-panel-pinTab",
+      "pageAction-panel-screenshots_mozilla_org",
+    ];
+    if (
+      AppConstants.platform == "macosx" ||
+      AppConstants.isPlatformAndVersionAtLeast("win", "6.4")
+    ) {
+      ids.push("pageAction-panel-shareURL");
+    }
+    for (let id of ids) {
+      let pref = `browser.engagement.${id}.used-count`;
+      let button = document.getElementById(id);
+      Assert.ok(button, `The button "${id}" should be present`);
+      Services.prefs.clearUserPref(pref);
+      Assert.equal(Services.prefs.getIntPref(pref, 0), 0, "Check initial");
+      click(button);
+      Assert.equal(Services.prefs.getIntPref(pref, 0), 1, "Check increment");
+      click(button);
+      Assert.equal(Services.prefs.getIntPref(pref, 0), 2, "Check increment");
+      Services.prefs.clearUserPref(pref);
+    }
+
+    let hidePromise = promisePageActionPanelHidden();
+    BrowserPageActions.panelNode.hidePopup();
+    await hidePromise;
+  });
+
+  await SpecialPowers.popPrefEnv();
+});