diff --git a/browser/components/migration/MigrationUtils.sys.mjs b/browser/components/migration/MigrationUtils.sys.mjs
index 6e3a473a5b78..3603000c3d0b 100644
--- a/browser/components/migration/MigrationUtils.sys.mjs
+++ b/browser/components/migration/MigrationUtils.sys.mjs
@@ -24,6 +24,7 @@ var gFileMigrators = null;
 var gProfileStartup = null;
 var gL10n = null;
 var gPreviousDefaultBrowserKey = "";
+var gHasOpenedLegacyWizard = false;
 
 let gForceExitSpinResolve = false;
 let gKeepUndoData = false;
@@ -689,6 +690,11 @@ class MigrationUtils {
       return Promise.resolve();
     }
     // Legacy migration dialog
+    if (!gHasOpenedLegacyWizard) {
+      gHasOpenedLegacyWizard = true;
+      aOptions.openedTime = Cu.now();
+    }
+
     const DIALOG_URL = "chrome://browser/content/migration/migration.xhtml";
     let features = "chrome,dialog,modal,centerscreen,titlebar,resizable=no";
     if (AppConstants.platform == "macosx" && !this.isStartupMigration) {
diff --git a/browser/components/migration/MigrationWizardParent.sys.mjs b/browser/components/migration/MigrationWizardParent.sys.mjs
index f81b09e9b464..1f18e9b8c18a 100644
--- a/browser/components/migration/MigrationWizardParent.sys.mjs
+++ b/browser/components/migration/MigrationWizardParent.sys.mjs
@@ -35,6 +35,12 @@ XPCOMUtils.defineLazyModuleGetters(lazy, {
   LoginCSVImport: "resource://gre/modules/LoginCSVImport.jsm",
 });
 
+/**
+ * Set to true once the first instance of MigrationWizardParent has received
+ * a "GetAvailableMigrators" message.
+ */
+let gHasOpenedBefore = false;
+
 /**
  * This class is responsible for communicating with MigrationUtils to do the
  * actual heavy-lifting of any kinds of migration work, based on messages from
@@ -75,6 +81,8 @@ export class MigrationWizardParent extends JSWindowActorParent {
 
     switch (message.name) {
       case "GetAvailableMigrators": {
+        let start = Cu.now();
+
         let availableMigrators = [];
         for (const key of MigrationUtils.availableMigratorKeys) {
           availableMigrators.push(this.#getMigratorAndProfiles(key));
@@ -98,6 +106,15 @@ export class MigrationWizardParent extends JSWindowActorParent {
             return b.lastModifiedDate - a.lastModifiedDate;
           });
 
+        let elapsed = Cu.now() - start;
+        if (!gHasOpenedBefore) {
+          gHasOpenedBefore = true;
+          Services.telemetry.scalarSet(
+            "migration.time_to_produce_migrator_list",
+            elapsed
+          );
+        }
+
         return filteredResults;
       }
 
diff --git a/browser/components/migration/content/migration.js b/browser/components/migration/content/migration.js
index bc27bb4c9d93..2804f53a29af 100644
--- a/browser/components/migration/content/migration.js
+++ b/browser/components/migration/content/migration.js
@@ -42,6 +42,7 @@ var MigrationWizard = {
   _autoMigrate: null,
   _receivedPermissions: new Set(),
   _succeededMigrationEventArgs: null,
+  _openedTime: null,
 
   init() {
     Services.telemetry.setEventRecordingEnabled("browser.migration", true);
@@ -71,6 +72,14 @@ var MigrationWizard = {
       .getHistogramById("FX_MIGRATION_ENTRY_POINT")
       .add(entryPointId);
 
+    // If the caller passed openedTime, that means this is the first time that
+    // the migration wizard is opening, and we want to measure its performance.
+    // Stash the time that opening was invoked so that we can measure the
+    // total elapsed time when the source list is shown.
+    if (args.openedTime) {
+      this._openedTime = args.openedTime;
+    }
+
     this.isInitialMigration =
       entrypoint == MigrationUtils.MIGRATION_ENTRYPOINTS.FIRSTRUN;
 
@@ -289,6 +298,17 @@ var MigrationWizard = {
       document.getElementById("importAll").hidden = true;
     }
 
+    // This must be the first time we're opening the migration wizard,
+    // and we want to know how long it took to get to this point, where
+    // we're showing the source list.
+    if (this._openedTime !== null) {
+      let elapsed = Cu.now() - this._openedTime;
+      Services.telemetry.scalarSet(
+        "migration.time_to_produce_legacy_migrator_list",
+        elapsed
+      );
+    }
+
     // Advance to the next page if the caller told us to.
     if (this._migrator && this._skipImportSourcePage) {
       this._wiz.advance();
diff --git a/browser/components/migration/tests/browser/browser_do_migration.js b/browser/components/migration/tests/browser/browser_do_migration.js
index 054f29c61029..fab9641960a7 100644
--- a/browser/components/migration/tests/browser/browser_do_migration.js
+++ b/browser/components/migration/tests/browser/browser_do_migration.js
@@ -54,6 +54,15 @@ add_task(async function test_successful_migrations() {
     ]);
   });
 
+  // We should make sure that the migration.time_to_produce_migrator_list
+  // scalar was set, since we know that at least one migration wizard has
+  // been opened.
+  let scalars = TelemetryTestUtils.getProcessScalars("parent", false, false);
+  Assert.ok(
+    scalars["migration.time_to_produce_migrator_list"] > 0,
+    "Non-zero scalar value recorded for migration.time_to_produce_migrator_list"
+  );
+
   // Scenario 2: Several resource types are available, but only 1
   // is checked / expected.
   migration = waitForTestMigration(
diff --git a/browser/components/migration/tests/browser/browser_entrypoint_telemetry.js b/browser/components/migration/tests/browser/browser_entrypoint_telemetry.js
index c8c529bc0d2f..f15082af3682 100644
--- a/browser/components/migration/tests/browser/browser_entrypoint_telemetry.js
+++ b/browser/components/migration/tests/browser/browser_entrypoint_telemetry.js
@@ -99,4 +99,13 @@ add_task(async function test_legacy_wizard() {
       TelemetryTestUtils.assertHistogram(legacyHistogram, entrypointId, 1);
     }
   }
+
+  // We should make sure that the migration.time_to_produce_legacy_migrator_list
+  // scalar was set, since we know that at least one legacy migration wizard has
+  // been opened.
+  let scalars = TelemetryTestUtils.getProcessScalars("parent", false, false);
+  Assert.ok(
+    scalars["migration.time_to_produce_legacy_migrator_list"] > 0,
+    "Non-zero scalar value recorded for migration.time_to_produce_migrator_list"
+  );
 });
diff --git a/toolkit/components/telemetry/Scalars.yaml b/toolkit/components/telemetry/Scalars.yaml
index 26729239228e..4e29dff07445 100644
--- a/toolkit/components/telemetry/Scalars.yaml
+++ b/toolkit/components/telemetry/Scalars.yaml
@@ -8348,6 +8348,36 @@ migration:
       - 'firefox'
     record_in_processes:
       - main
+  time_to_produce_legacy_migrator_list:
+    bug_numbers:
+      - 1840917
+    description: >
+      The amount of time it took in milliseconds to produce the list of migrators in the
+      legacy migration wizard.
+    expires: never
+    kind: uint
+    notification_emails:
+      - mconley@mozilla.com
+    release_channel_collection: opt-out
+    products:
+      - 'firefox'
+    record_in_processes:
+      - main
+  time_to_produce_migrator_list:
+    bug_numbers:
+      - 1840917
+    description: >
+      The amount of time it took in milliseconds to produce the list of migrators and profiles
+      for the first time the migration wizard opened during the process lifetime.
+    expires: never
+    kind: uint
+    notification_emails:
+      - mconley@mozilla.com
+    release_channel_collection: opt-out
+    products:
+      - 'firefox'
+    record_in_processes:
+      - main
 
 contextual.services.topsites:
   impression: