Born in New Haven, Connecticut, she was raised in Guilford, Connecticut. She began performing musicals and plays at local theaters, and studied at the University of Pennsylvania, where she graduated with a BA in European History. She then moved to New York City and landed several roles in television commercials. She was also featured as writer and host for a celebrity interview show on TBS called "Movie Junky".

She currently plays the role of Amanda Tanen in the comedy-drama series, Ugly Betty, and, with co-star and personal friend Michael Urie, is co-host of the Official Ugly Betty Podcast. In the episode "Sofia's Choice," Newton did a dual role as Ruthie, a frumpy assistant at another magazine. In the episode "Secretaries' Day" she parodied her infamous Olive Garden commercial by having her alter ego Amanda show off a video resume that featured the receptionist performing as a "Serving Wench" in a commercial for a medieval-themed restaurant during her pre-MODE days as an ac