Staff at the University of Bradford have begun a three-day strike in a row over plans to axe jobs.
Unison said its members had walked out because of "management's refusal to communicate the number of jobs" being cut.
It said dozens were on the picket line dressed in Halloween costumes "to highlight the horrors" facing about 250 administration and support workers.
The university had said a decrease in student applications led to the cuts.
Leonie Sharp, Unison's regional organiser, said the union wanted "a halt to the restructure and a guarantee of no job cuts".
"Unison members in professional support roles at the University of Bradford have had enough of restructures and redundancies that have cut support services for students by 20%. Today they say 'no more'."
Ms Sharp said the strike action, which affected cleaners and security workers, would run for three consecutive days and also on Tuesday.
"Students understand we're doing it for them. Nobody wants disruption for students but nobody wants a university cut to the bare bones."
In a statement, the University of Bradford said: "The Higher Education sector has become market driven and increasingly competitive.
"In order to remain financially viable and sustainable, we, along with other institutions, will continue to innovate, evolve and reshape internally.
"Against this backdrop, we have set a clear plan for the university's development over the next two to three years. We are on track to deliver this plan."
A spokeswoman said the university was doing "everything we can to minimise any impact on the student experience".
"The university's senior management has been in consultation with the unions to try to avert strike action, and remains committed to fully engaging with them," she added.
Earlier this year, vice-chancellor Brian Cantor said the university was experiencing a decrease in applications from the UK and as a result of changes to the government's funding arrangements.
The university has about 1,650 staff and about 9,800 students were enrolled for the 2017-18 academic year.