diff --git a/includes/classes/Indexable/User/User.php b/includes/classes/Indexable/User/User.php
index c72b0110f0..40136f9367 100644
--- a/includes/classes/Indexable/User/User.php
+++ b/includes/classes/Indexable/User/User.php
@@ -129,7 +129,25 @@ public function format_args( $query_vars, $query ) {
 		 * Support `role` query arg
 		 */
 		if ( ! empty( $blog_id ) ) {
-			if ( ! empty( $query_vars['role'] ) ) {
+			// If a blog id is set, we will apply at least one filter for roles.
+			$use_filters = true;
+
+			// If there are no specific roles named, make sure the user is a member of the site.
+			if ( empty( $query_vars['role'] ) && empty( $query_vars['role__in'] ) && empty( $query_vars['role__not_in'] ) ) {
+				$filter['bool']['must'][]     = array(
+					'exists' => array(
+						'field' => 'capabilities.' . $blog_id . '.roles',
+					),
+				);
+				/**
+				 * EP versions prior to 4.1.0 set non-existent roles as `0`.
+				 */
+				$filter['bool']['must_not'][] = array(
+					'term' => array(
+						'capabilities.' . $blog_id . '.roles' => 0,
+					),
+				);
+			} elseif ( ! empty( $query_vars['role'] ) ) {
 				$roles = (array) $query_vars['role'];
 
 				foreach ( $roles as $role ) {
@@ -141,8 +159,6 @@ public function format_args( $query_vars, $query ) {
 						),
 					);
 				}
-
-				$use_filters = true;
 			} else {
 				if ( ! empty( $query_vars['role__in'] ) ) {
 					$roles_in = (array) $query_vars['role__in'];
@@ -154,8 +170,6 @@ public function format_args( $query_vars, $query ) {
 							'capabilities.' . $blog_id . '.roles' => $roles_in,
 						),
 					);
-
-					$use_filters = true;
 				}
 
 				if ( ! empty( $query_vars['role__not_in'] ) ) {
@@ -170,8 +184,6 @@ public function format_args( $query_vars, $query ) {
 							),
 						);
 					}
-
-					$use_filters = true;
 				}
 			}
 		}
@@ -864,7 +876,7 @@ public function prepare_capabilities( $user_id ) {
 
 			if ( ! empty( $roles ) ) {
 				$prepared_roles[ (int) $site['blog_id'] ] = [
-					'roles' => array_keys( $roles ),
+					'roles' => array_keys( (array) $roles ),
 				];
 			}
 		}
diff --git a/tests/cypress/integration/indexables/user.spec.js b/tests/cypress/integration/indexables/user.spec.js
index 1e33486084..b4e8c45119 100644
--- a/tests/cypress/integration/indexables/user.spec.js
+++ b/tests/cypress/integration/indexables/user.spec.js
@@ -104,4 +104,49 @@ describe('User Indexable', () => {
 				expect(text).to.contain('"value": "Doe"');
 			});
 	});
+
+	it('Only returns users from the current blog', () => {
+		cy.login();
+
+		cy.maybeEnableFeature('users');
+
+		const newUserData = {
+			userLogin: 'nobloguser',
+			userEmail: 'no-blog-user@example.com',
+		};
+
+		cy.wpCli(`wp user get ${newUserData.userLogin} --field=ID`, true).then((wpCliResponse) => {
+			if (wpCliResponse.code === 0) {
+				cy.wpCli(`wp user delete ${newUserData.userLogin} --yes --network`);
+				cy.wpCli('wp elasticpress index --setup --yes');
+			}
+		});
+
+		// Create a user without a blog.
+		cy.visitAdminPage('network/user-new.php');
+		cy.get('#username').clearThenType(newUserData.userLogin);
+		cy.get('#email').clearThenType(newUserData.userEmail);
+		cy.get('#add-user').click();
+		cy.get('#message.updated').should('be.visible');
+
+		// Searching for it should not return anything.
+		searchUser('nobloguser');
+		cy.get('.wp-list-table').should('contain.text', 'No users found.');
+		cy.getTotal(0);
+		cy.get('.ep-query-debug').should('contain.text', 'Query Response Code: HTTP 200');
+
+		// Add user to the blog.
+		cy.visitAdminPage('user-new.php');
+		cy.get('#adduser-email').clearThenType(newUserData.userLogin);
+		cy.get('#adduser-noconfirmation').check();
+		cy.get('#addusersub').click();
+		cy.get('#message.updated').should('be.visible');
+
+		// Searching for it should return it.
+		searchUser('nobloguser');
+		cy.get('.wp-list-table').should('contain.text', 'nobloguser');
+		cy.getTotal(1);
+		cy.get('.ep-query-debug').should('contain.text', 'Query Response Code: HTTP 200');
+		cy.get('.query-results').should('contain.text', '"user_email": "no-blog-user@example.com"');
+	});
 });
diff --git a/tests/php/indexables/TestUser.php b/tests/php/indexables/TestUser.php
index 7cfacfb101..464a3e7a0d 100644
--- a/tests/php/indexables/TestUser.php
+++ b/tests/php/indexables/TestUser.php
@@ -1439,4 +1439,58 @@ public function testIntegrateSearchQueries() {
 
 		$this->assertTrue( $this->get_feature()->integrate_search_queries( false, $query ) );
 	}
+
+	/**
+	 * Test users that does not belong to any blog.
+	 *
+	 * @since 4.1.0
+	 */
+	public function testUserSearchLimitedToOneBlog() {
+		// This user does not belong to any blog.
+		Functions\create_and_sync_user(
+			[
+				'user_login'   => 'users-and-blogs-1',
+				'role'         => '',
+				'first_name'   => 'No Blog',
+				'last_name'    => 'User',
+				'user_email'   => 'no-blog@test.com',
+				'user_url'     => 'http://domain.test',
+			]
+		);
+		Functions\create_and_sync_user(
+			[
+				'user_login'   => 'users-and-blogs-2',
+				'role'         => 'contributor',
+				'first_name'   => 'Blog',
+				'last_name'    => 'User',
+				'user_email'   => 'blog@test.com',
+				'user_url'     => 'http://domain.test',
+			]
+		);
+
+		ElasticPress\Elasticsearch::factory()->refresh_indices();
+
+		// Here `blog_id` defaults to `get_current_blog_id()`.
+		$query = new \WP_User_Query( [
+			'search' => 'users-and-blogs'
+		] );
+
+		$this->assertTrue( $this->get_feature()->integrate_search_queries( false, $query ) );
+		$this->assertEquals( 1, $query->total_users );
+		foreach ( $query->results as $user ) {
+			$this->assertTrue( $user->elasticsearch );
+		}
+
+		// Search accross all blogs.
+		$query = new \WP_User_Query( [
+			'search'  => 'users-and-blogs',
+			'blog_id' => 0,
+		] );
+
+		$this->assertTrue( $this->get_feature()->integrate_search_queries( false, $query ) );
+		$this->assertEquals( 2, $query->total_users );
+		foreach ( $query->results as $user ) {
+			$this->assertTrue( $user->elasticsearch );
+		}
+	}
 }