diff --git a/CHANGELOG.md b/CHANGELOG.md
index 49fec306dc8..319fa5a9a7c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@
 - Fixed type definitions around `EuiI18n`'s `default` prop to better support use cases ([#1861](https://github.com/elastic/eui/pull/1861))
 - Localized `EuiTablePagination`'s row count selection ([#1883](https://github.com/elastic/eui/pull/1883))
 - Fixed `EuiComboBox` with `singleSelection` and `onAddCustomOption` reopening the options list after adding a custom option ([#1882](https://github.com/elastic/eui/pull/1882))
+- Fixed `EuiComboBox` reopening the options list in Firefox when closing via the dropdown arrow button ([#1885](https://github.com/elastic/eui/pull/1885))
 
 ## [`10.1.0`](https://github.com/elastic/eui/tree/v10.1.0)
 
diff --git a/src/components/combo_box/combo_box.js b/src/components/combo_box/combo_box.js
index 26e3fdc0165..405f28ce1a7 100644
--- a/src/components/combo_box/combo_box.js
+++ b/src/components/combo_box/combo_box.js
@@ -303,8 +303,11 @@ export class EuiComboBox extends Component {
 
   onContainerBlur = (e) => {
     // close the options list, unless the use clicked on an option
-    const focusedInOptionsList = this.optionsList && this.optionsList.contains(e.relatedTarget);
-    const focusedInInput = this.comboBox && this.comboBox.contains(e.relatedTarget);
+
+    // FireFox returns `relatedTarget` as `null` for security reasons, but provides a proprietary `explicitOriginalTarget`
+    const relatedTarget = e.relatedTarget || e.explicitOriginalTarget;
+    const focusedInOptionsList = relatedTarget && this.optionsList && this.optionsList.contains(relatedTarget);
+    const focusedInInput = relatedTarget && this.comboBox && this.comboBox.contains(relatedTarget);
     if (!focusedInOptionsList && !focusedInInput) {
       this.closeList();