Born in Washington, D.C., Chasanow received a Bachelor of Arts degree from Rutgers University in 1970 and a Juris Doctor from Stanford Law School in 1974.

She was a law clerk for David L. Cahoon, Montgomery County Circuit Court, Maryland from 1974 to 1975, and was in private practice in Washington, D.C. in 1975.

On August 6, 1993, Chasanow was nominated by President Bill Clinton to a seat on the United States District Court for the District of Maryland vacated by Alexander Harvey II.

She became chief judge in 2010, serving in that capacity until she assumed senior status on October 3, 2014.

[2] In November 2015, Chasanow found that the Bladensburg Peace Cross war memorial did not violate the Constitution's Establishment Clause.