Systems and methods are provided for positioning an isolation device within a multilateral well to isolate a live wellbore from other wellbores in the well system. The isolation device can be changed from an open position to a closed position substantially contemporaneously to the wellbore becoming a live wellbore. Another procedure can be performed on the other wellbore of the multilateral well while the isolation device is in the closed position. A tubing string or a short or intermediate completion string can isolate a wellbore from pressure applied to another wellbore within the multilateral system. The tubing string or the short or intermediate completion string may also isolate a junction area of the multilateral well system.