The Westchester County district attorney says 53-year-old Margo Reed was arraigned Wednesday in Yonkers City Court on a charge of grand larceny.
Reed was responsible for collecting overdue fines and other revenue from the library's three branches and depositing the money.
The district attorney says that on several occasions from 2004 to 2010, Reed took some of the money and altered records to cover the theft.
Reed was represented by Legal Aid, which hasn't returned a telephone call seeking comment.
Reed could be sentenced to five to 15 years in prison if convicted.