A Mixed Unit often consist of two different troop types, with one or more handlers that drive the rest of the unit forward. The handler(s) must be deployed in the rear rank(s) of the unit, as centrally as possible. Mixed Units cannot be joined by characters, unless specified. If a character is allowed to join a Mixed Unit, they may choose if they want to be placed in the front or rear rank.

If a Mixed unit is required to take a characteristic test, this is done using the characteristics of the unit itself, not the handlers. The only exception is Leadership tests, which are taken using the unit's highest Leadership value. When the models in a unit with the Mixed Unit special rule have different Movement allowances, the handlers' Movement value is ignored, unless they are the only models remaining. Any special rules or upgrades that the unit might have do not apply to the Handlers unless specified. Note that if the unit has the Expendable, Swiftstride or Vanguard special rules, this also applies to the Handlers.

As long as the unit (but not the handlers) have a Unit Strength of 5 or more, any missile hits are resolved against the unit itself. At less than Unit Strength 5, there is a chance that any handlers in the unit could be hit – the controlling player decides who is hit, but must allocate one hit on each model before they can add a second hit on a model; they must allocate two hits on each model before they can allocate a third, and so on. Hits from templates are resolved against the handlers as normal. In close combat, the handlers can only be attacked by models who are in base contact with them.