diff --git a/tools/windows/DatadogAgentInstaller/CustomActions.Tests/ProcessUserCustomActions/ProcessUserCustomActionsDomainClientTests.cs b/tools/windows/DatadogAgentInstaller/CustomActions.Tests/ProcessUserCustomActions/ProcessUserCustomActionsDomainClientTests.cs
index 0f39fd84b1bc3..05f506c8c5e5f 100644
--- a/tools/windows/DatadogAgentInstaller/CustomActions.Tests/ProcessUserCustomActions/ProcessUserCustomActionsDomainClientTests.cs
+++ b/tools/windows/DatadogAgentInstaller/CustomActions.Tests/ProcessUserCustomActions/ProcessUserCustomActionsDomainClientTests.cs
@@ -70,7 +70,7 @@ public void ProcessDdAgentUserCredentials_Succeeds_With_Custom_Existing_Domain_U
             Test.WithDomainUser(ddAgentUserName);
 
             Test.Session
-                .Setup(session => session["DDAGENTUSER_NAME"]).Returns($"{Domain}\\{ddAgentUserName}");
+                .Setup(session => session["DDAGENTUSER_NAME"]).Returns($"{Domain}@{ddAgentUserName}");
             Test.Session
                 .Setup(session => session["DDAGENTUSER_PASSWORD"]).Returns(ddAgentUserPassword);
 
diff --git a/tools/windows/DatadogAgentInstaller/CustomActions/ProcessUserCustomActions.cs b/tools/windows/DatadogAgentInstaller/CustomActions/ProcessUserCustomActions.cs
index 090e8cc92b0c0..6e3263cc3b17f 100644
--- a/tools/windows/DatadogAgentInstaller/CustomActions/ProcessUserCustomActions.cs
+++ b/tools/windows/DatadogAgentInstaller/CustomActions/ProcessUserCustomActions.cs
@@ -1,5 +1,6 @@
 using System;
 using System.DirectoryServices.ActiveDirectory;
+using System.Linq;
 using System.Security.Cryptography;
 using System.Security.Principal;
 using System.Windows.Forms;
@@ -170,9 +171,9 @@ private void ParseUserName(string account, out string userName, out string domai
             // We do not use CredUIParseUserName because it does not handle some cases nicely.
             // e.g. CredUIParseUserName(host.ddev.net\user) returns userName=.ddev.net domain=host.ddev.net
             // e.g. CredUIParseUserName(.\user) returns userName=.\user domain=
-            if (account.Contains("\\"))
+            var sepChars = new[] { '\\', '@' };
+            foreach (var parts in sepChars.Where(account.Contains).Select(s => account.Split(s)))
             {
-                var parts = account.Split('\\');
                 domain = parts[0];
                 userName = parts[1];
                 if (NameUsesDefaultPart(domain))