Downes was born in Liverpool, England. She has appeared in nearly all of the British lad mags, and has been on the cover of Loaded, Maxim, Nuts, and Zoo Weekly. Nuts Magazine ranked her 11th sexiest on their list 50 Hottest Blondes of 2008, placing her higher than other glamour models Amy Diamond and model Rhian Sugden.

She had a cameo appearance in the movie Deuce Bigalow: European Gigolo as a window washer in a wet white t-shirt. In the movie's special features, Downes is seen auditioning for the role against Page Three models Michelle Marsh, Nicola Tappenden, and Nikkala Stott.

Katie Downes appeared in the reality television series Poor Little Rich Girls on ITV where for a week she swapped her life as model with a young woman named Michelle McManus who worked as a toilet cleaner.

Katie confirmed she was, in fact, an Everton F.C. supporter.[citation needed]

Katie Downes has been romantically linked by the British media to Arctic Monkeys guitarist Jamie Cook since 2006.