Austin was born Denise Katnich in San Pedro, California. She started gymnastics at the age of 12, which led to an athletic scholarship at the University of Arizona.

In 1983, Denise married sports attorney Jeff Austin, brother of US Open champion Tracy Austin. Denise and Jeff have two daughters, Kelly (b. 1990) and Katie (b. 1993). The Austin family resides in Alexandria, Virginia.

Austin initially attended the University of Arizona on a gymnastics scholarship, reaching the rank of No. 9 in the NCAA on balance beam. She later transferred to California State University, Long Beach, graduating with a bachelor's degree in physical education, and a minor in exercise physiology.