Janine Gibson, a senior editor at The Guardian who oversaw coverage that won the newspaper its first Pulitzer Prize but who was recently passed over when a new editor in chief was appointed, is leaving the organization.

Ms. Gibson had been at The Guardian for 17 years, said Jennifer Lindenauer, a spokeswoman for the newspaper. Her departure, she said, “is very amicable. We wish her the best.” No reason was supplied, and Ms. Gibson did not respond to a message seeking comment. Her departure was first reported by Politico.

Ms. Gibson joined the Guardian in 1998 and held various jobs, including media editor and editor of its website. She later became the editor in chief of the Guardian’s American operations, where she oversaw coverage based on documents leaked by the former National Security Agency contractor Edward J. Snowden. Those articles won the Pulitzer Prize for public service last year, an honor shared with The Washington Post.

It was widely reported last year that Ms. Gibson had been a hiring target for The New York Times and that tension over her potential role at The Times had been a factor in the dismissal of Jill Abramson, The Times’s executive editor.