Yes, you can grant admin privileges to users from an external organization (such as your marketing agency) without needing to create a new user account in your own Google Workspace, which would require an additional license. You can do this by using the "Admin role delegation" feature with Google Workspace domain sharing.

Here are the steps to delegate admin access to an external user without creating a new user:

1. Set Up Trusted Domain Sharing (Optional)

• If you want to grant full admin access to someone in an external Google Workspace domain, you need to ensure trusted domain sharing is enabled:
  • Go to the Admin Console.
  • Navigate to Account → Account settings → External collaboration settings.
  • Ensure that trusted domains are allowed, and add the marketing agency’s Google Workspace domain as a trusted domain.

2. Delegate Admin Roles to the External User

• Instead of adding them as a new user, follow these steps to delegate roles to their existing email address (from their own Google Workspace domain):
  1. In your Admin Console, go to Directory → Users.
  2. Under Admin roles, find and click on the role you wish to delegate (e.g., Super Admin, Custom Admin Role).
  3. Click Assign users.
  4. Enter the email address of the external user (e.g., their work email address from their own domain) in the Assign users field.
  5. Assign the appropriate admin role you want the marketing agency to have.

3. Grant API and Services Access (Optional)

• If they need to access specific services (e.g., Google Ads, Analytics, etc.), ensure the right permissions are delegated at the service level (e.g., granting API access to their tools).
  • Go to Security → API controls → Manage domain-wide delegation.
  • Add the third-party agency's domain and configure the necessary access.

4. Review Security and Permissions

• Ensure that your security policies (e.g., 2-Step Verification, OAuth controls) are in place for external users to minimize any risks of unauthorized access.

5. Monitor Activity and Access

• Regularly audit their activities to ensure they are using the privileges appropriately. You can view the Admin audit logs in your Google Workspace to track any actions they take.

By doing this, you avoid paying for an additional Google Workspace license and ensure the marketing agency can manage your account using their existing credentials.