She began her tenure on September 1, 2012, joining The New York Times from The Buffalo News, where she had been editor and vice-president.

[3] She graduated from Nardin Academy in Buffalo, where she served as editor in chief of the school newspaper and captain of the basketball team.

Sullivan focused The Buffalo News's reporting on poverty, economic development and inequities in public education and established its first investigative team.

[13] In February 2016, it was announced that when Sullivan left The Times, she would be joining The Washington Post as its media columnist.

[14] Arthur Sulzberger Jr., The Times's publisher, praised Sullivan in a memo to staff stating that she had "ushered the position into a new age."

On August 10, 2022, Sullivan announced her departure in memo to staff, calling it a "self-imposed term limit".

[19] On Jan. 1, 2024, Sullivan began her role as executive director for the Craig Newmark Center for Journalism Ethics and Security at Columbia University.

[21][22] The same year she won the Penn State University Bart Richards Award for Media Criticism.