Beaty was born in Centennial, Colorado. While living in Denver, Madisen performed in over 65 theater shows. She played Lindsay in an Ad Council's PSA on Cyber-Bullying. She also protrayed Daisy at age 10 in the film The Curious Case of Benjamin Button. Beaty also starred in the independent film The Five. Beaty plays Sara Dougan in 2010 Lifetime movie, The Pregnancy Pact alongside Thora Birch. Beaty played Leslie in the iCarly episode, "iWas a Pageant Girl". Beaty played Kristin Haskell in the NCIS episode, "Dead Air". For this role, she won the Young Artist Award's Best Performance in a TV Series Guest Starring Young Actress award. In 2012, she appeared in The Master, a Paul Thomas Anderson film starring Phillip Seymour Hoffman, Joaquin Phoenix, and Amy Adams.