Ostroff began her career in news as a reporter for WINZ, a CBS affiliate in Miami. She also worked in local news at WPLG and WTVJ in Miami. She later held senior positions at 20th Century Fox, Michael Jacobs Productions and the Kushner-Locke Company. From 2002 to 2006, Ostroff served as president of the UPN Network, a subsidiary of CBS, where she developed the popular reality series America’s Next Top Model, along with other programs including Veronica Mars, , WWE SmackDown, Girlfriends, Moesha, Everybody Hates Chris and Dilbert. From 1996 to 2002, she served as executive vice president of entertainment at Lifetime Television and led the network to rise from sixth to become the #1-rated cable network in prime time. Beginning in 2006, Ostroff was president of entertainment for The CW broadcast network - a joint venture of CBS and Warner Bros. Ostroff was in charge of programming, digital initiatives, branding, marketing, research and sales. As president, she developed several TV series, including Gossip Girl and The Vampire Diaries. Ostroff and Condé Nast CEO Bob Sauerberg co-founded and launched Condé Nast Entertainment in 2011, a studio and distribution network for film, television, premium digital video, social, and virtual reality. At CNE, Ostroff produced film projects including Only the Brave, adapted from a GQ feature; The First Monday in May; The Old Man & the Gun with Robert Redford as well as TV series including Last Chance U on Netflix and Vanity Fair Confidential on Investigation Discovery. Additionally, through its digital franchises, such as Vogue's “73 Questions” and WIRED's “Autocomplete Interview,” CNE made 5,000 videos, garnering more than 11 billion views in 2017. Ostroff joined Spotify in August 2018. She leads all aspects of content and distribution operations, including global advertising, global original content, content marketing, industry and creator relationships, and licensing. Under her leadership, the streaming platform has grown with playlists including Viva Latino; and expanded into other forms of audio, primarily podcasts. She also helped in the platform's acquisition of Gimlet Media. Ostroff serves on the Board of New York University College of Arts & Science. She has also served on the Board of Directors for Westfield Corporation and on the City Year LA board. In June 2020, Activision Blizzard appointed her to its board as an independent director.