She is also the niece of teen idol and executive producer Shaun Cassidy. Katie grew up in the Los Angeles suburb of Calabasas and was active in tumbling and cheerleading. She also performed in community theatre productions and studied with an acting coach. As a teen she did some modeling, eventually working on a campaign for Abercrombie and Fitch. She attended Calabasas High School and graduated with honors.
Regarding having relatives in the entertainment industry, Katie Cassidy said, It definitely got me in the door, but at the end of the day no one is going to hire you because you are a celebritys offspring. You have to be talented. It does get you more opportunities at first.
In 2002, Artemis Records signed her to cover her fathers hit, I Think I Love You. The song helped make Katie a star.
Katie Cassidys first role was in The Division. Other roles followed, including parts in New Girl, 7th Heaven, Supernatural, Harpers Island, Gossip Girl, and Melrose Place, among others. She has made appearances in the films Click, Taken, and A Nightmare on Elm Street, and more.
She said of her character in Click, It was really funny because one of the jokes is that she grows up and she has gigantic boobs and obviouslyIm not really like that, so they literally had all this stuffing in me and it was so painful (askmen.com).
Katie Cassidy said about her character on Melrose Place, I have to be ready to make out with women or have a threesome. I need to be ready for anything. Its all part of the game though. Being an actor, a character might have an element or two that might be uncomfortable for you. But Im not playing Katie Cassidy. Im playing Ella Simms and that is part of her. You have to be able to take on anything, and I was open to it. It sounds fun! (snmag.com).
Of her part in horror movies, Katie added, Its definitely draining emotionally, but its like running a marathon, youve got to be ready for those two months of your life. At the end of the day Im so tired. I just go home and sleep, wake up and do the same thing over and over. But ultimately, in the end, its well worth it.
As far as singing, Katie Cassidy said, Singing was never really my thing. Maybe Ill do a musical. Acting is really where my heart is.
In 2012, Katie Cassidy landed on The CW series Arrow.
Katie is a spokesperson for the charity H.E.L.P. Malawi.