Fox was born in Lawrenceville, Georgia. She moved to Westlake, Ohio at age 4. A year later her mother put Rachel and her sister into a theater program to make sure they were comfortable with public speaking. She began doing commercials and print work in Ohio and was represented by Ford Modeling Agency and The Docherty Agency. She appeared in print for American Greetings, Target, and JoAnn Fabrics. She appeared in the Lite House Pools and Spas TV commercial and various regional commercials. Fox moved to California at the age of 9. She is currently schooled at Chaminade College Preparatory.
In July 2009, Fox filmed the movie Spork, which was released in 2010 which would be her first lead movie role. She also starred in Jim Sheridan'sDream House, portraying Chloe Patterson, daughter of Ann and Jack Patterson (played by Naomi Watts and Marton Csokas, respectively).
Fox on Stocks, launched in 2012 and said to be Fox's stock-trading blog, describes her as "a very successful stock trader in her free time," and says that it "provides education for those wishing to learn more about investing."