The University of Sydney is investigating more than 20 staff for financial misconduct.

Fairfax Media understands the university is auditing expenditure estimated at tens of thousands of dollars for entertainment including birthday cakes, coffees, alcohol and stationery.

The staff being questioned work in student administration and recruitment, which generates more than $1 billion a year in revenue for the university.

A spokeswoman for the university told Fairfax Media that 21 staff members were being questioned in relation to allegations of financial misconduct.

"The University takes any allegation of financial misconduct seriously," the spokeswoman said.