diff --git a/docs/documentation/upgrading/topics/changes/changes-26_5_0.adoc b/docs/documentation/upgrading/topics/changes/changes-26_5_0.adoc
index 52bad946f56..4f3d760c770 100644
--- a/docs/documentation/upgrading/topics/changes/changes-26_5_0.adoc
+++ b/docs/documentation/upgrading/topics/changes/changes-26_5_0.adoc
@@ -171,6 +171,14 @@ See the link:{upgradingguide_link}[{upgradingguide_name}] for details on how to
 For each expired user session there is a new user event `USER_SESSION_DELETED` fired.
 As part of this change, the process now deletes rows from the table in small batches, instead of issuing a delete statements that affects the whole table. This should allow for better response times when there are a lot of sessions in the table.
 
+=== Organization custom attribute named 'id' behavior change
+
+Organizations can have custom attributes named `id`. When both organization attributes and organization ID are included in tokens via the organization membership mapper configuration,
+the organization ID will override any custom `id` attribute value. Previously, the organization ID was added first and could be overridden by custom attributes.
+This ensures that the `id` field in the organization claims always contains the actual organization ID.
+
+If you have a custom organization attribute named `id` and rely on its value in tokens, you should rename the attribute to avoid it being overridden by the organization ID.
+
 // ------------------------ Deprecated features ------------------------ //
 == Deprecated features
 
diff --git a/services/src/main/java/org/keycloak/organization/protocol/mappers/oidc/OrganizationMembershipMapper.java b/services/src/main/java/org/keycloak/organization/protocol/mappers/oidc/OrganizationMembershipMapper.java
index dc34f0d6105..923eeb8ca3f 100644
--- a/services/src/main/java/org/keycloak/organization/protocol/mappers/oidc/OrganizationMembershipMapper.java
+++ b/services/src/main/java/org/keycloak/organization/protocol/mappers/oidc/OrganizationMembershipMapper.java
@@ -162,12 +162,14 @@ public class OrganizationMembershipMapper extends AbstractOIDCProtocolMapper imp
 
             Map<String, Object> claims = new HashMap<>();
 
-            if (isAddOrganizationId(model)) {
-                claims.put(OAuth2Constants.ORGANIZATION_ID, o.getId());
-            }
+            // Add organization attributes first
             if (isAddOrganizationAttributes(model)) {
                 claims.putAll(o.getAttributes());
             }
+            // Add organization ID last so it overrides any custom "id" attribute
+            if (isAddOrganizationId(model)) {
+                claims.put(OAuth2Constants.ORGANIZATION_ID, o.getId());
+            }
 
             value.put(o.getAlias(), claims);
         }
diff --git a/testsuite/integration-arquillian/tests/base/src/test/java/org/keycloak/testsuite/organization/mapper/OrganizationOIDCProtocolMapperTest.java b/testsuite/integration-arquillian/tests/base/src/test/java/org/keycloak/testsuite/organization/mapper/OrganizationOIDCProtocolMapperTest.java
index 77d8d4c0f0f..c939d990201 100644
--- a/testsuite/integration-arquillian/tests/base/src/test/java/org/keycloak/testsuite/organization/mapper/OrganizationOIDCProtocolMapperTest.java
+++ b/testsuite/integration-arquillian/tests/base/src/test/java/org/keycloak/testsuite/organization/mapper/OrganizationOIDCProtocolMapperTest.java
@@ -79,8 +79,8 @@ public class OrganizationOIDCProtocolMapperTest extends AbstractOrganizationTest
 
     @Before
     public void onBefore() {
-        setMapperConfig(OIDCAttributeMapperHelper.JSON_TYPE, null);
         setMapperConfig(ProtocolMapperUtils.MULTIVALUED, null);
+        setMapperConfig(OIDCAttributeMapperHelper.JSON_TYPE, null);
     }
 
     @Test
@@ -984,6 +984,41 @@ public class OrganizationOIDCProtocolMapperTest extends AbstractOrganizationTest
         assertThat(organization, containsInAnyOrder("orga", "orgb"));
     }
 
+    @Test
+    @SuppressWarnings("unchecked")
+    public void testOrganizationAttributeNamedIdIsOverriddenByOrganizationId() throws Exception {
+        // When an organization has a custom attribute called "id", the organization ID should override it in tokens
+        OrganizationRepresentation orgRep = createOrganization();
+        OrganizationResource organization = testRealm().organizations().get(orgRep.getId());
+        addMember(organization);
+        
+        // Add a custom attribute named "id" to the organization
+        orgRep.singleAttribute("id", "custom-id-value");
+        
+        try (Response response = organization.update(orgRep)) {
+            assertEquals(Status.NO_CONTENT.getStatusCode(), response.getStatus());
+        }
+        
+        // Verify that organization ID overrides custom "id" attribute in tokens
+        setMapperConfig(OrganizationMembershipMapper.ADD_ORGANIZATION_ID, Boolean.TRUE.toString());
+        setMapperConfig(OrganizationMembershipMapper.ADD_ORGANIZATION_ATTRIBUTES, Boolean.TRUE.toString());
+
+        oauth.client("direct-grant", "password");
+        oauth.scope("openid organization");
+        AccessTokenResponse response = oauth.doPasswordGrantRequest(memberEmail, memberPassword);
+        assertThat(response.getScope(), containsString("organization"));
+        AccessToken accessToken = TokenVerifier.create(response.getAccessToken(), AccessToken.class).getToken();
+        assertThat(accessToken.getOtherClaims().keySet(), hasItem(OAuth2Constants.ORGANIZATION));
+        
+        Map<String, Map<String, String>> organizations = (Map<String, Map<String, String>>) accessToken.getOtherClaims().get(OAuth2Constants.ORGANIZATION);
+        assertThat(organizations.keySet(), hasItem(organizationName));
+        Map<String, String> orgClaims = organizations.get(organizationName);
+        
+        // The "id" attribute should contain the organization ID, not the custom value
+        assertThat(orgClaims.get("id"), equalTo(orgRep.getId()));
+        assertThat(orgClaims.get("id"), not(equalTo("custom-id-value")));
+    }
+
     private AccessTokenResponse assertSuccessfulCodeGrant() {
         String code = oauth.parseLoginResponse().getCode();
         AccessTokenResponse response = oauth.doAccessTokenRequest(code);