diff --git a/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/components/agent_policy_advanced_fields/index.tsx b/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/components/agent_policy_advanced_fields/index.tsx
index 1497b1bb0589e..6b0a7c512d197 100644
--- a/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/components/agent_policy_advanced_fields/index.tsx
+++ b/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/components/agent_policy_advanced_fields/index.tsx
@@ -53,7 +53,7 @@ import { UninstallCommandFlyout } from '../../../../../../components';
 import type { ValidationResults } from '../agent_policy_validation';
 
 import { ExperimentalFeaturesService } from '../../../../services';
-
+import { useAgentPolicyFormContext } from '../agent_policy_form';
 import { policyHasEndpointSecurity as hasElasticDefend } from '../../../../../../../common/services';
 
 import {
@@ -127,6 +127,8 @@ export const AgentPolicyAdvancedOptionsContent: React.FunctionComponent<Props> =
   const isManagedorAgentlessPolicy =
     agentPolicy.is_managed === true || agentPolicy?.supports_agentless === true;
 
+  const agentPolicyFormContect = useAgentPolicyFormContext();
+
   const AgentTamperProtectionSectionContent = useMemo(
     () => (
       <EuiDescribedFormGroup
@@ -325,32 +327,23 @@ export const AgentPolicyAdvancedOptionsContent: React.FunctionComponent<Props> =
             />
           }
         >
-          <EuiFormRow
-            fullWidth
-            key="space"
-            error={
-              touchedFields.description && validation.description ? validation.description : null
-            }
+          <SpaceSelector
             isDisabled={disabled}
-            isInvalid={Boolean(touchedFields.description && validation.description)}
-          >
-            <SpaceSelector
-              isDisabled={disabled}
-              value={
-                'space_ids' in agentPolicy && agentPolicy.space_ids
-                  ? agentPolicy.space_ids
-                  : [spaceId || 'default']
+            value={
+              'space_ids' in agentPolicy && agentPolicy.space_ids
+                ? agentPolicy.space_ids
+                : [spaceId || 'default']
+            }
+            setInvalidSpaceError={agentPolicyFormContect?.setInvalidSpaceError}
+            onChange={(newValue) => {
+              if (newValue.length === 0) {
+                return;
               }
-              onChange={(newValue) => {
-                if (newValue.length === 0) {
-                  return;
-                }
-                updateAgentPolicy({
-                  space_ids: newValue,
-                });
-              }}
-            />
-          </EuiFormRow>
+              updateAgentPolicy({
+                space_ids: newValue,
+              });
+            }}
+          />
         </EuiDescribedFormGroup>
       ) : null}
       <EuiDescribedFormGroup
diff --git a/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/components/agent_policy_advanced_fields/space_selector.test.tsx b/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/components/agent_policy_advanced_fields/space_selector.test.tsx
new file mode 100644
index 0000000000000..bd90fd8fd6a3e
--- /dev/null
+++ b/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/components/agent_policy_advanced_fields/space_selector.test.tsx
@@ -0,0 +1,90 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import React from 'react';
+import { fireEvent } from '@testing-library/react';
+
+import { useAgentPoliciesSpaces } from '../../../../../../hooks/use_request/spaces';
+
+import { createFleetTestRendererMock } from '../../../../../../mock';
+
+import { SpaceSelector } from './space_selector';
+
+jest.mock('../../../../../../hooks/use_request/spaces');
+
+describe('Space Selector', () => {
+  beforeEach(() => {
+    jest.mocked(useAgentPoliciesSpaces).mockReturnValue({
+      data: {
+        items: [
+          {
+            name: 'Default',
+            id: 'default',
+          },
+          {
+            name: 'Test',
+            id: 'test',
+          },
+        ],
+      },
+    } as any);
+  });
+  function render() {
+    const renderer = createFleetTestRendererMock();
+    const onChange = jest.fn();
+    const setInvalidSpaceError = jest.fn();
+    const result = renderer.render(
+      <SpaceSelector setInvalidSpaceError={setInvalidSpaceError} onChange={onChange} value={[]} />
+    );
+
+    return {
+      result,
+      onChange,
+      setInvalidSpaceError,
+    };
+  }
+
+  it('should render invalid space errors', () => {
+    const { result, onChange, setInvalidSpaceError } = render();
+    const inputEl = result.getByTestId('comboBoxSearchInput');
+    fireEvent.change(inputEl, {
+      target: { value: 'invalidSpace' },
+    });
+    fireEvent.keyDown(inputEl, { key: 'Enter', code: 'Enter' });
+    expect(result.container).toHaveTextContent('invalidSpace is not a valid space.');
+    expect(onChange).not.toBeCalled();
+    expect(setInvalidSpaceError).toBeCalledWith(true);
+  });
+
+  it('should clear invalid space errors', () => {
+    const { result, setInvalidSpaceError } = render();
+    const inputEl = result.getByTestId('comboBoxSearchInput');
+    fireEvent.change(inputEl, {
+      target: { value: 'invalidSpace' },
+    });
+    fireEvent.keyDown(inputEl, { key: 'Enter', code: 'Enter' });
+    expect(result.container).toHaveTextContent('invalidSpace is not a valid space.');
+    fireEvent.change(inputEl, {
+      target: { value: '' },
+    });
+    fireEvent.keyDown(inputEl, { key: 'Enter', code: 'Enter' });
+    expect(result.container).not.toHaveTextContent('invalidSpace is not a valid space.');
+    expect(setInvalidSpaceError).toBeCalledWith(false);
+  });
+
+  it('should accept valid space', () => {
+    const { result, onChange, setInvalidSpaceError } = render();
+    const inputEl = result.getByTestId('comboBoxSearchInput');
+    fireEvent.change(inputEl, {
+      target: { value: 'test' },
+    });
+    fireEvent.keyDown(inputEl, { key: 'Enter', code: 'Enter' });
+    expect(result.container).not.toHaveTextContent('test is not a valid space.');
+    expect(onChange).toBeCalledWith(['test']);
+    expect(setInvalidSpaceError).not.toBeCalledWith(true);
+  });
+});
diff --git a/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/components/agent_policy_advanced_fields/space_selector.tsx b/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/components/agent_policy_advanced_fields/space_selector.tsx
index 0532c5306d50f..53c7ed1d8226d 100644
--- a/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/components/agent_policy_advanced_fields/space_selector.tsx
+++ b/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/components/agent_policy_advanced_fields/space_selector.tsx
@@ -5,7 +5,7 @@
  * 2.0.
  */
 
-import { type EuiComboBoxOptionOption, EuiHealth } from '@elastic/eui';
+import { type EuiComboBoxOptionOption, EuiHealth, EuiFormRow } from '@elastic/eui';
 import { EuiComboBox } from '@elastic/eui';
 import { i18n } from '@kbn/i18n';
 import React, { useMemo } from 'react';
@@ -16,11 +16,19 @@ export interface SpaceSelectorProps {
   value: string[];
   onChange: (newVal: string[]) => void;
   isDisabled?: boolean;
+  setInvalidSpaceError?: (hasError: boolean) => void;
 }
 
-export const SpaceSelector: React.FC<SpaceSelectorProps> = ({ value, onChange, isDisabled }) => {
+export const SpaceSelector: React.FC<SpaceSelectorProps> = ({
+  setInvalidSpaceError,
+  value,
+  onChange,
+  isDisabled,
+}) => {
   const res = useAgentPoliciesSpaces();
 
+  const [error, setError] = React.useState<string>();
+
   const renderOption = React.useCallback(
     (option: any, searchValue: string, contentClassName: string) => (
       <EuiHealth color={option.color}>
@@ -57,20 +65,41 @@ export const SpaceSelector: React.FC<SpaceSelectorProps> = ({ value, onChange, i
   }, [options, value, res.isInitialLoading]);
 
   return (
-    <EuiComboBox
-      data-test-subj={'spaceSelectorComboBox'}
-      aria-label={i18n.translate('xpack.fleet.agentPolicies.spaceSelectorLabel', {
-        defaultMessage: 'Spaces',
-      })}
+    <EuiFormRow
       fullWidth
-      options={options}
-      renderOption={renderOption}
-      selectedOptions={selectedOptions}
-      isDisabled={res.isInitialLoading || isDisabled}
-      isClearable={false}
-      onChange={(newOptions) => {
-        onChange(newOptions.map(({ key }) => key as string));
-      }}
-    />
+      key="space"
+      error={error}
+      isDisabled={isDisabled}
+      isInvalid={Boolean(error)}
+    >
+      <EuiComboBox
+        data-test-subj={'spaceSelectorComboBox'}
+        aria-label={i18n.translate('xpack.fleet.agentPolicies.spaceSelectorLabel', {
+          defaultMessage: 'Spaces',
+        })}
+        fullWidth
+        options={options}
+        renderOption={renderOption}
+        selectedOptions={selectedOptions}
+        isDisabled={res.isInitialLoading || isDisabled}
+        isClearable={false}
+        onSearchChange={(searchValue, hasMatchingOptions) => {
+          const newError =
+            searchValue.length === 0 || hasMatchingOptions
+              ? undefined
+              : i18n.translate('xpack.fleet.agentPolicies.spaceSelectorInvalid', {
+                  defaultMessage: '{space} is not a valid space.',
+                  values: { space: searchValue },
+                });
+          setError(newError);
+          if (setInvalidSpaceError) {
+            setInvalidSpaceError(!!newError);
+          }
+        }}
+        onChange={(newOptions) => {
+          onChange(newOptions.map(({ key }) => key as string));
+        }}
+      />
+    </EuiFormRow>
   );
 };
diff --git a/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/components/agent_policy_form.tsx b/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/components/agent_policy_form.tsx
index b437d61f64c58..8e97afcaa4d66 100644
--- a/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/components/agent_policy_form.tsx
+++ b/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/components/agent_policy_form.tsx
@@ -45,12 +45,14 @@ interface Props {
   isEditing?: boolean;
   // form error state is passed up to the form
   updateAdvancedSettingsHasErrors: (hasErrors: boolean) => void;
+  setInvalidSpaceError: (hasErrors: boolean) => void;
 }
 const AgentPolicyFormContext = React.createContext<
   | {
       agentPolicy: Partial<NewAgentPolicy | AgentPolicy> & { [key: string]: any };
       updateAgentPolicy: (u: Partial<NewAgentPolicy | AgentPolicy>) => void;
       updateAdvancedSettingsHasErrors: (hasErrors: boolean) => void;
+      setInvalidSpaceError: (hasErrors: boolean) => void;
     }
   | undefined
 >(undefined);
@@ -67,6 +69,7 @@ export const AgentPolicyForm: React.FunctionComponent<Props> = ({
   validation,
   isEditing = false,
   updateAdvancedSettingsHasErrors,
+  setInvalidSpaceError,
 }) => {
   const authz = useAuthz();
   const isDisabled = !authz.fleet.allAgentPolicies;
@@ -97,7 +100,12 @@ export const AgentPolicyForm: React.FunctionComponent<Props> = ({
 
   return (
     <AgentPolicyFormContext.Provider
-      value={{ agentPolicy, updateAgentPolicy, updateAdvancedSettingsHasErrors }}
+      value={{
+        agentPolicy,
+        updateAgentPolicy,
+        updateAdvancedSettingsHasErrors,
+        setInvalidSpaceError,
+      }}
     >
       <EuiForm>
         {!isEditing ? (
diff --git a/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/details_page/components/settings/index.tsx b/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/details_page/components/settings/index.tsx
index 6e4f1e06b45a0..91cd710db4343 100644
--- a/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/details_page/components/settings/index.tsx
+++ b/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/details_page/components/settings/index.tsx
@@ -90,6 +90,7 @@ export const SettingsView = memo<{ agentPolicy: AgentPolicy }>(
       allowedNamespacePrefixes: spaceSettings?.allowedNamespacePrefixes,
     });
     const [hasAdvancedSettingsErrors, setHasAdvancedSettingsErrors] = useState<boolean>(false);
+    const [hasInvalidSpaceError, setInvalidSpaceError] = useState<boolean>(false);
 
     const updateAgentPolicy = (updatedFields: Partial<AgentPolicy>) => {
       setAgentPolicy({
@@ -183,6 +184,7 @@ export const SettingsView = memo<{ agentPolicy: AgentPolicy }>(
           validation={validation}
           isEditing={true}
           updateAdvancedSettingsHasErrors={setHasAdvancedSettingsErrors}
+          setInvalidSpaceError={setInvalidSpaceError}
         />
 
         {hasChanges ? (
@@ -219,7 +221,8 @@ export const SettingsView = memo<{ agentPolicy: AgentPolicy }>(
                           isDisabled={
                             isLoading ||
                             Object.keys(validation).length > 0 ||
-                            hasAdvancedSettingsErrors
+                            hasAdvancedSettingsErrors ||
+                            hasInvalidSpaceError
                           }
                           btnProps={{
                             color: 'text',
@@ -242,7 +245,8 @@ export const SettingsView = memo<{ agentPolicy: AgentPolicy }>(
                           !hasAllAgentPoliciesPrivileges ||
                           isLoading ||
                           Object.keys(validation).length > 0 ||
-                          hasAdvancedSettingsErrors
+                          hasAdvancedSettingsErrors ||
+                          hasInvalidSpaceError
                         }
                         data-test-subj="agentPolicyDetailsSaveButton"
                         iconType="save"
diff --git a/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/list_page/components/create_agent_policy.tsx b/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/list_page/components/create_agent_policy.tsx
index f147f7e112ea1..a5538e7e0fa30 100644
--- a/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/list_page/components/create_agent_policy.tsx
+++ b/x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/list_page/components/create_agent_policy.tsx
@@ -61,6 +61,7 @@ export const CreateAgentPolicyFlyout: React.FunctionComponent<Props> = ({
     allowedNamespacePrefixes: spaceSettings?.allowedNamespacePrefixes,
   });
   const [hasAdvancedSettingsErrors, setHasAdvancedSettingsErrors] = useState<boolean>(false);
+  const [hasInvalidSpaceError, setInvalidSpaceError] = useState<boolean>(false);
 
   const updateAgentPolicy = (updatedFields: Partial<NewAgentPolicy>) => {
     setAgentPolicy({
@@ -104,6 +105,7 @@ export const CreateAgentPolicyFlyout: React.FunctionComponent<Props> = ({
         updateSysMonitoring={(newValue) => setWithSysMonitoring(newValue)}
         validation={validation}
         updateAdvancedSettingsHasErrors={setHasAdvancedSettingsErrors}
+        setInvalidSpaceError={setInvalidSpaceError}
       />
     </EuiFlyoutBody>
   );
@@ -130,7 +132,10 @@ export const CreateAgentPolicyFlyout: React.FunctionComponent<Props> = ({
               <EuiFlexItem grow={false}>
                 <DevtoolsRequestFlyoutButton
                   isDisabled={
-                    isLoading || Object.keys(validation).length > 0 || hasAdvancedSettingsErrors
+                    isLoading ||
+                    Object.keys(validation).length > 0 ||
+                    hasAdvancedSettingsErrors ||
+                    hasInvalidSpaceError
                   }
                   description={i18n.translate(
                     'xpack.fleet.createAgentPolicy.devtoolsRequestDescription',
@@ -150,7 +155,8 @@ export const CreateAgentPolicyFlyout: React.FunctionComponent<Props> = ({
                   !hasFleetAllAgentPoliciesPrivileges ||
                   isLoading ||
                   Object.keys(validation).length > 0 ||
-                  hasAdvancedSettingsErrors
+                  hasAdvancedSettingsErrors ||
+                  hasInvalidSpaceError
                 }
                 onClick={async () => {
                   setIsLoading(true);