diff --git a/x-pack/plugins/fleet/public/applications/fleet/sections/agents/components/agent_upgrade_modal/index.tsx b/x-pack/plugins/fleet/public/applications/fleet/sections/agents/components/agent_upgrade_modal/index.tsx
index 34cf9085d78a5..888fa4874e1c8 100644
--- a/x-pack/plugins/fleet/public/applications/fleet/sections/agents/components/agent_upgrade_modal/index.tsx
+++ b/x-pack/plugins/fleet/public/applications/fleet/sections/agents/components/agent_upgrade_modal/index.tsx
@@ -16,6 +16,7 @@ import {
   EuiIcon,
   EuiFlexGroup,
   EuiFlexItem,
+  EuiCallOut
 } from '@elastic/eui';
 import { FormattedMessage } from '@kbn/i18n-react';
 
@@ -43,6 +44,8 @@ export const AgentUpgradeAgentModal: React.FunctionComponent<Props> = ({
 }) => {
   const { notifications } = useStartServices();
   const [isSubmitting, setIsSubmitting] = useState(false);
+  const [errors, setErrors] = useState<string | undefined>();
+
   const isSingleAgent = Array.isArray(agents) && agents.length === 1;
   const isSmallBatch = Array.isArray(agents) && agents.length > 1 && agents.length <= 10;
   const isAllAgents = agents === '';
@@ -97,6 +100,9 @@ export const AgentUpgradeAgentModal: React.FunctionComponent<Props> = ({
             ...rolloutOptions,
           });
       if (error) {
+        if (error?.statusCode === 400) {
+          setErrors(error?.message);
+        }
         throw error;
       }
 
@@ -128,7 +134,6 @@ export const AgentUpgradeAgentModal: React.FunctionComponent<Props> = ({
               isAllAgents,
             },
           });
-      // remove toasts
       if (counts.success === counts.total) {
         notifications.toasts.addSuccess(successMessage);
       } else if (counts.error === counts.total) {
@@ -231,6 +236,7 @@ export const AgentUpgradeAgentModal: React.FunctionComponent<Props> = ({
         fullWidth
       >
         <EuiComboBox
+          data-test-subj="agentUpgradeModal.VersionCombobox"
           fullWidth
           singleSelection={{ asPlainText: true }}
           options={fallbackVersions}
@@ -270,6 +276,7 @@ export const AgentUpgradeAgentModal: React.FunctionComponent<Props> = ({
           fullWidth
         >
           <EuiComboBox
+            data-test-subj="agentUpgradeModal.MaintainanceCombobox"
             fullWidth
             singleSelection={{ asPlainText: true }}
             options={maintainanceOptions}
@@ -280,6 +287,25 @@ export const AgentUpgradeAgentModal: React.FunctionComponent<Props> = ({
           />
         </EuiFormRow>
       ) : null}
+      { errors ?
+        <>
+          <EuiCallOut
+            color="danger"
+            title={
+              i18n.translate('xpack.fleet.upgradeAgents.warningCallout', {
+                defaultMessage:
+                  'Error upgrading the selected {count, plural, one {agent} other {{count} agents}}',
+                values: { count: isSingleAgent },
+              })
+            }
+          >
+            <FormattedMessage
+              id="xpack.fleet.deleteAgentPolicy.confirmModal.affectedAgentsMessage"
+              defaultMessage={errors}
+            />
+          </EuiCallOut>
+        </> : null
+      }
     </EuiConfirmModal>
   );
 };
diff --git a/x-pack/plugins/translations/translations/fr-FR.json b/x-pack/plugins/translations/translations/fr-FR.json
index af4f20d80b563..1cc5d4da738a7 100644
--- a/x-pack/plugins/translations/translations/fr-FR.json
+++ b/x-pack/plugins/translations/translations/fr-FR.json
@@ -13073,8 +13073,6 @@
     "xpack.fleet.upgradeAgents.cancelButtonLabel": "Annuler",
     "xpack.fleet.upgradeAgents.confirmMultipleButtonLabel": "Mettre à niveau {count, plural, one {l'agent} other {{count} agents} =true {tous les agents sélectionnés}}",
     "xpack.fleet.upgradeAgents.confirmSingleButtonLabel": "Mettre à niveau l'agent",
-    "xpack.fleet.upgradeAgents.experimentalLabel": "Expérimental",
-    "xpack.fleet.upgradeAgents.experimentalLabelTooltip": "Une modification ou une suppression de la mise à niveau de l'agent peut intervenir dans une version ultérieure. La mise à niveau n'est pas soumise à l'accord de niveau de service du support technique.",
     "xpack.fleet.upgradeAgents.fatalErrorNotificationTitle": "Erreur lors de la mise à niveau de {count, plural, one {l'agent} other {{count} agents} =true {tous les agents sélectionnés}}",
     "xpack.fleet.upgradeAgents.successMultiNotificationTitle": "{isMixed, select, true {{success} agents sur {total}} other {{isAllAgents, select, true {Tous les agents sélectionnés} other {{success}} }}} mis à niveau",
     "xpack.fleet.upgradeAgents.successSingleNotificationTitle": "{count} agent mis à niveau",
diff --git a/x-pack/plugins/translations/translations/ja-JP.json b/x-pack/plugins/translations/translations/ja-JP.json
index 8123876ede978..fa17fbceea882 100644
--- a/x-pack/plugins/translations/translations/ja-JP.json
+++ b/x-pack/plugins/translations/translations/ja-JP.json
@@ -13190,8 +13190,6 @@
     "xpack.fleet.upgradeAgents.cancelButtonLabel": "キャンセル",
     "xpack.fleet.upgradeAgents.confirmMultipleButtonLabel": "{count, plural, other  {{count}個のエージェント} =true {すべての選択されたエージェント}}をアップグレード",
     "xpack.fleet.upgradeAgents.confirmSingleButtonLabel": "エージェントをアップグレード",
-    "xpack.fleet.upgradeAgents.experimentalLabel": "実験的",
-    "xpack.fleet.upgradeAgents.experimentalLabelTooltip": "アップグレードエージェントは今後のリリースで変更または削除される可能性があり、SLA のサポート対象になりません。",
     "xpack.fleet.upgradeAgents.fatalErrorNotificationTitle": "{count, plural, other  {{count}個のエージェント} =true {すべての選択されたエージェント}}のアップグレードエラー",
     "xpack.fleet.upgradeAgents.successMultiNotificationTitle": "{isMixed, select, true {{success}/{total}個の} other {{isAllAgents, select, true {すべての選択された} other {{success}} }}}エージェントをアップグレードしました",
     "xpack.fleet.upgradeAgents.successSingleNotificationTitle": "{count}個のエージェントをアップグレードしました",
diff --git a/x-pack/plugins/translations/translations/zh-CN.json b/x-pack/plugins/translations/translations/zh-CN.json
index 2b06479908b6e..5e4715a040826 100644
--- a/x-pack/plugins/translations/translations/zh-CN.json
+++ b/x-pack/plugins/translations/translations/zh-CN.json
@@ -13214,8 +13214,6 @@
     "xpack.fleet.upgradeAgents.cancelButtonLabel": "取消",
     "xpack.fleet.upgradeAgents.confirmMultipleButtonLabel": "升级{count, plural, one {代理} other { {count} 个代理} =true {所有选定代理}}",
     "xpack.fleet.upgradeAgents.confirmSingleButtonLabel": "升级代理",
-    "xpack.fleet.upgradeAgents.experimentalLabel": "实验性",
-    "xpack.fleet.upgradeAgents.experimentalLabelTooltip": "在未来的版本中可能会更改或移除升级代理，其不受支持 SLA 的约束。",
     "xpack.fleet.upgradeAgents.fatalErrorNotificationTitle": "升级{count, plural, one {代理} other { {count} 个代理} =true {所有选定代理}}时出错",
     "xpack.fleet.upgradeAgents.successMultiNotificationTitle": "已升级{isMixed, select, true { {success} 个（共 {total} 个）} other {{isAllAgents, select, true {所有选定} other { {success} 个} }}}代理",
     "xpack.fleet.upgradeAgents.successSingleNotificationTitle": "已升级 {count} 个代理",