The extent of job losses needed to address a £30m black hole in its budget is not yet clear, Cardiff University's vice-chancellor has said.
A voluntary redundancy scheme at Wales' biggest university closed last month but Prof Wendy Larner said she did not have definite numbers of post closures and did not rule out compulsory job losses.
A union said staff faced "stress" and "anxiety" and it comes as Bangor University wrote to its staff offering voluntary severance after a drop in student numbers.
The Welsh government said it was monitoring universities at a "challenging financial period".
Most of Wales' institutions have announced measures to address financial pressures at an "existential moment" for the sector, which is facing growing costs and reduced income from international students.
Prof Larner said cutting staff costs was only one part of the plan to address a deficit of £32.8m and save about £9m, but the final numbers were not yet clear.
"At this stage we are not talking about compulsory redundancies," she added.
"But given how quickly things are changing in the sector around us... of course, I can't rule it out."
She said a recruitment freeze would continue "until we get our financial house in order".
The Cardiff University branch of the University and College Union said staff faced "stress, anxiety and an uncertain future" and called for the institution's leaders to fight for better funding for higher education.
"We are appalled to hear the vice-chancellor fail to reassure her staff on compulsory redundancies," branch president Dr Joey Whitfield said, promising a ballot of members on industrial action if such a step was taken.
But Prof Larner said the university's strategy was about "qualitative change, not just quantitative change" which would involve developing new sources of income and different ways of delivering courses.
She said there would be more international partnerships to run courses and usage of the university's buildings was being reviewed.
In an email to staff on Wednesday, Bangor University outlined its measures to address "unprecedented financial pressures," saying it faced a £9m deficit this year.
It said student numbers were below budgeted numbers, including a 7% reduction in UK undergraduates compared to last year and a 50% drop in postgraduate international students.
Deputy vice-chancellor Prof Andrew Edwards said a £250 increase in tuition fees did not go far enough to meet extra costs.
"The funding model has to be looked at," he added.
Meanwhile a minister was forced to clarify comments made in the Senedd about a "transformation fund" for the sector.
Vikki Howells, the further and higher education minister, wrote to the Llywydd, Elin Jones, after making reference to a fund in response to a question in the chamber on Tuesday.
"I would like to clarify that the policy in this area remains at a very exploratory stage, and we are still working through what, if any, potential support mechanism may look like", she said.
She added that the government "do not believe there is any Welsh institution that is at risk of failure".
The Welsh government said it had increased the tuition fee limit from £9,000 to £9,250.
It said the financial position of universities was being monitored by Medr, the new institution responsible for funding the sector, and Ms Howells met universities regularly.