City Department of Health spokesman James Garrow said Wednesday there are 15 confirmed cases and 59 probable cases, all but three of them in Philadelphia. Probable diagnoses indicate a person showing mumps-like symptoms.
Students have been lining up all week at walk-in clinics to get vaccinated for free.
The city says the numbers reported this year are high compared with those in past years; 54 cases were reported in 2010.
Students who may be infected should limit contact with others and seek medical care.
Mumps is a viral infection that involves swollen glands. The Centers for Disease Control and Prevention say the measles-mumps-rubella vaccine is the best protection.
Mumps vaccine has been part of routine childhood shots for decades, but research suggests that protection fades 10 or more years after the second dose.