The £135 million expansion of Glasgow University had been predicted by the principal to be completed in a decade.
Announcing the project in February, Professor Anton Muscatelli said the Gilmorehill site would be developed "over the next 10 years".
However, a Glasgow City Council report, which was rubber stamped by decision makers yesterday, suggested it could be 2035 before the campus is ready for students.
The 'Final Draft Campus Development Framework' stated: "The transformation of the university campus, including the former Western Infirmary site will take time, likely 5-20 years."
Ann Allen, Director of Estates at Glasgow University, admitted the process will be carried out piecemeal.
She said: "The Campus Development Framework (CDF) provides a framework for redevelopment which will take time to deliver - the document indicates up to 20 years.
"The University Court will consider the full Estate Strategy at their Autumn meeting. This strategy will be a 10-year plan and will identify which buildings will be delivered first.
"The CDF provides the framework under which these decisions can be made, however the university will still need planning approval for each individual development and we will continue to consult on all proposals.
"Once the strategy is approved we will be able to make clear statements on timelines for delivery."
Ms Allen also revealed that hundreds of local residents have given their views on the multi-million pounds project.
She said: "The CDF is an important first step in the development of the Gilmorehill Strategy. It has been developed over the course of the last year.
"There has been extensive consultation during this period and the university is extremely grateful for the contribution of the West End community - more than 3600 people commented during the third stage of the consultation."
Glasgow University chiefs are expected to spend at least £80m on new buildings and £55m refurbishing some existing structures.
The 10-acre site, which includes the Western Infirmary, will be off-loaded by the NHS next year, when the new South Glasgow Hospital opens.
The plans were given the green light by councillors who sit on the city's executive committee yesterday.
A spokesman for the council said: "The University of Glasgow's ambitious plans for the Gilmorehill campus are very exciting, and we look forward to working with them on the redevelopment.
"The various projects on this site will bring tremendous benefit to both the university and the city."
In 1878 the university transferred the land to the former Hospital Authority to construct the original Western Infirmary.
The terms of the deal stipulated that should the site no longer be required for healthcare purposes, the university should be given the opportunity to reacquire it.