Braddy was born on August 30, 1987 in Atlanta, Georgia; the daughter of Jo Beth, a preschool music teacher and a vocalist, and Steve Braddy, an engineer. Johanna Braddy has one brother, Cole Braddy, who is eight years younger. Braddy attended the McIntosh High School in Peachtree City, Georgia, and graduated in 2005. Johanna was also the captain of her high school dance team. She was an active member of McIntosh's drama program under director Stephen Buckner.
Braddy's film debut was in the film Pop Rocks playing Olivia Harden. Her television debut was in Avatar: The Last Airbender playing the Princess Yue being a major/secondary character. Braddy has appeared in other roles such as Surf's Up, Broken Bridges, Home of the Giants, The Oaks, and many more film and television roles including her role on Greek as new ZBZ pledge Jordan. She also played Lisa in Paranormal Activity 3 and The Grudge 3 and Melody Bostic in the 2010 comedy Easy A. Later, Braddy co-starred as Anna Martin in the Lifetime dark comedy-drama series, UnREAL.