University pro-vice chancellor of humanities Prof Tony Ballantyne said the departments to undergo a formal management of change process were anthropology and archaeology, English and linguistics, history (with probable cuts in art history), languages and cultures, and music.
Meetings for staff in departments to be reviewed were held yesterday to ensure the process was clear, Prof Ballantyne said.
The management of change process was "genuinely consultative'' and staff had the opportunity to respond to proposed changes to staff levels.
"It is only after we work through the consultation phase that any change begins to be implemented.
"We hope that we can work through these processes carefully but promptly for the five impacted units ... by November.''
Figures obtained under the Official Information Act show the divisions under review have experienced drops in EFTS (equivalent full-time students) since 2012.
The humanities division had experienced a "sustained decline'' in student numbers since 2010, from 5900 EFTS to about 4800, he said.
"That is a significant reduction and it has real implications.
"Many of our academic units, but not all by any means, have lost a considerable percentage of students and as a result they are often costing a lot more to operate than the income they generate.''
It was crucial to review staffing levels and student numbers to ensure the future of the division, he said.
He did not know how many jobs would be cut, but said 15-20 was not an unrealistic "ball park figure''.
A management of change process was likely to occur in the College of Education early next year, and the philosophy, social work and classics programmes would be monitored, and if necessary, undergo management of change processes at the end of 2017.
Students enrolled in programmes that would undergo management of change processes would be supported by the university and allowed to complete their study, Prof Ballantyne said.
Otago University Students Association vice-president Jarred Griffiths said the association was concerned by any cuts to humanities.
"We think the humanities department plays a massive role as the critic and conscience of society.''
The association would monitor the situation closely and offer support to any students who wanted it, he said.