How can I prevent agents in one group from seeing another group's tickets?

Can I restrict agent access to tickets within their groups?

Yes, to ensure agents in one group do not view tickets from another group, create a private ticket group. When a group is private, only agents from that group view its tickets.

If your plan doesn't include private ticket groups, choose from two alternatives:

Option 1: Keep one Zendesk account

The benefit of a single account is to keep all agents in the same account with a single subscription. A single account also maintains all settings and admins. However, agents may circumvent the separation and each admin has access to data from all groups.

In addition, restrict agent access with groups

For Support, Suite Team, Growth, and Professional plans, set Access to Tickets in agent's groups in the agent profile

For Enterprise plans, select Within their groups under Tickets they can access. in the custom role for the agent

Depending on the use case, the flexibility from this workaround is desirable: Can I use the same Support account for customer support and HR workflows?

Option 2: With two Zendesk accounts

Setting up two separate Zendesk accounts:

Provides an even more secure way to separate agents and it's the preferred method when data privacy is the primary concern. It provides a flexible long-term solution because users can modify workflows.

However, two accounts would require two subscriptions and more initial setup effort.

To share a ticket between two instances:

Set up an agreement to share tickets between both accounts.

This agreement grants another account permission to work on tickets.

The other account accesses only shared tickets.