Karrie Kristina Hamilton was born in McAllen, Texas at McAllen Medical Hospital. She was the third child born to South Texas ranchers George (Buck) Hamilton and Sharon Jones. Her father has ranched in Duval county since the 1970s and served as a Sheriff's deputy in Duval, Jim Hogg and McMullen Counties. Her mother was a registered nurse at McAllen Medical Hospital and owned her own home health agency. At the age of 2, Karrie learned how to ride horses and started competing in rodeos at age 3. She continued to competitively rodeo for over 10 years. She played varsity basketball, softball and volleyball at Hebbronville High School. Karrie was recruited by East Texas Baptist University to play volleyball. She was pre-med and graduated with a major in Biology and minor in Chemistry. Upon graduation, she decided not to pursue medicine and instead chose a career in film. Cox has appeared in numerous independent films including Blade of the King, Something Good, The Good Wife and Out of the Darkness. In 2007 Cox co-founded Through Films, an independent film production company in Austin, Texas. Through Films was formed as a vehicle for Cox's writing and acting. In 2008, Karrie wrote, directed and produced her first film Los Encinos. She is splitting her time between Los Angeles and Austin where she continues to write and act.

Majored in Biology with a Minor in Chemistry; She chose to pursue acting after college instead of medicine.