diff --git a/src/Core/Services/Implementations/OrganizationService.cs b/src/Core/Services/Implementations/OrganizationService.cs
index b7424a53e..069916803 100644
--- a/src/Core/Services/Implementations/OrganizationService.cs
+++ b/src/Core/Services/Implementations/OrganizationService.cs
@@ -410,6 +410,11 @@ public class OrganizationService : IOrganizationService
         var secretsManagerPlan = StaticStore.SecretManagerPlans.FirstOrDefault(p => p.Type == signup.Plan);
         if (signup.UseSecretsManager)
         {
+            if (provider)
+            {
+                throw new BadRequestException(
+                    "Organizations with a Managed Service Provider do not support Secrets Manager.");
+            }
             ValidateSecretsManagerPlan(secretsManagerPlan, signup);
         }
 
diff --git a/test/Core.Test/Services/OrganizationServiceTests.cs b/test/Core.Test/Services/OrganizationServiceTests.cs
index 01073f4d2..54efee118 100644
--- a/test/Core.Test/Services/OrganizationServiceTests.cs
+++ b/test/Core.Test/Services/OrganizationServiceTests.cs
@@ -262,6 +262,22 @@ public class OrganizationServiceTests
         );
     }
 
+    [Theory]
+    [BitAutoData(PlanType.EnterpriseAnnually)]
+    public async Task SignUp_SM_Throws_WhenManagedByMSP(PlanType planType, OrganizationSignup signup, SutProvider<OrganizationService> sutProvider)
+    {
+        signup.Plan = planType;
+        signup.UseSecretsManager = true;
+        signup.AdditionalSeats = 15;
+        signup.AdditionalSmSeats = 10;
+        signup.AdditionalServiceAccounts = 20;
+        signup.PaymentMethodType = PaymentMethodType.Card;
+        signup.PremiumAccessAddon = false;
+
+        var exception = await Assert.ThrowsAsync<BadRequestException>(() => sutProvider.Sut.SignUpAsync(signup, true));
+        Assert.Contains("Organizations with a Managed Service Provider do not support Secrets Manager.", exception.Message);
+    }
+
     [Theory]
     [BitAutoData]
     public async Task SignUpAsync_SecretManager_AdditionalServiceAccounts_NotAllowedByPlan_ShouldThrowException(OrganizationSignup signup, SutProvider<OrganizationService> sutProvider)