He served as NUS' provost and deputy president from 2004, before being made senior deputy president last year, where he took charge of the university's strategic plans and its budgets.
A kidney specialist, he joined NUS as a lecturer in the Department of Medicine in 1987 and became the university's youngest dean at the age of 38 in 1997.
He also served as director of medical services at the Ministry of Health from 2000 to 2004.
Prof Tan received the Public Service Star award in 2003 for his role in leading the public health response to the severe acute respiratory syndrome (Sars) crisis in Singapore.