Queen's University Belfast (QUB) and Ulster University (UU) face three further days of strike action by some staff at the end of November.
The University and College Union (UCU), which represents lecturers and support staff, is taking the action over pay, working conditions and pensions.
Union members were previously out on strike for 10 days in February and March.
Staff at 70 UK universities plan to walk out on 24, 25 and 30 November.
That includes QUB and UU in Northern Ireland as well as the Open University.
Union members do not have to inform universities in advance if they will strike so it is not clear how many classes or lectures will be cancelled.
It is also not known exactly how many staff at QUB and UU will strike, but UCU is a union with hundreds of members at both universities.
